[PATCH v3 6/6] drivers:pci:hv: New paravirtual PCI front-end for Hyper-V VMs

[jakeo]

From: Jake Oshins <jakeo@xxxxxxxxxxxxx>

This patch supplies a new driver, hv_pcifront, which exposes new root PCI
buses.  When a Hyper-V VM running Linux is offered a paravirtual PCI bus
in order to expose a device passed through on that bus, this drver
registers a new bus with the PCI driver.  This new bus is bus "zero"
within a new PCI domain.  This is done so that there's no overlap between
the emulated, or fully virtualized, PCI that may be in the VM and a real
PCIe device that will be exposed.

This PCI front-end only supports PCIe devices which do not use I/O BARs and
which do not need a legacy INTx# interrupt (relying on MSI or MSI-X).
Multifunction devices are supported, but devices with Type 1 or Type 2
config headers are not supported.  (These are bridges to other PCI buses.)

The content of this patch differs from the one sent previously in that it
incorporates feedback related to unused code (which has been removed) and
GPL license (which has been updated.)  It also removes Kconfig lines that
had been copied from the Xen PCI front-end entry, but which shouldn't be
used here.

Signed-off-by: Jake Oshins <jakeo@xxxxxxxxxxxxx>
---
 MAINTAINERS                    |    1 +
 drivers/pci/Kconfig            |    7 +
 drivers/pci/host/Makefile      |    1 +
 drivers/pci/host/hv_pcifront.c | 2101 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 2110 insertions(+)
 create mode 100644 drivers/pci/host/hv_pcifront.c

diff --git a/MAINTAINERS b/MAINTAINERS
index d8afd29..ed8d991 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4759,6 +4759,7 @@ F:	arch/x86/kernel/cpu/mshyperv.c
 F:	drivers/hid/hid-hyperv.c
 F:	drivers/hv/
 F:	drivers/input/serio/hyperv-keyboard.c
+F:	drivers/pci/host/hv_pcifront.c
 F:	drivers/net/hyperv/
 F:	drivers/scsi/storvsc_drv.c
 F:	drivers/video/fbdev/hyperv_fb.c
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 7a8f1c5..3ee97a9 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -114,4 +114,11 @@ config PCI_LABEL
 	def_bool y if (DMI || ACPI)
 	select NLS
 
+config HYPERV_VPCI
+        tristate "Hyper-V PCI Frontend"
+        depends on PCI && X86 && HYPERV
+        help
+          The PCI device frontend driver allows the kernel to import arbitrary
+          PCI devices from a PCI backend to support PCI driver domains.
+
 source "drivers/pci/host/Kconfig"
diff --git a/drivers/pci/host/Makefile b/drivers/pci/host/Makefile
index f733b4e..7bf8442 100644
--- a/drivers/pci/host/Makefile
+++ b/drivers/pci/host/Makefile
@@ -2,6 +2,7 @@ obj-$(CONFIG_PCIE_DW) += pcie-designware.o
 obj-$(CONFIG_PCI_DRA7XX) += pci-dra7xx.o
 obj-$(CONFIG_PCI_EXYNOS) += pci-exynos.o
 obj-$(CONFIG_PCI_IMX6) += pci-imx6.o
+obj-$(CONFIG_HYPERV_VPCI) += hv_pcifront.o
 obj-$(CONFIG_PCI_MVEBU) += pci-mvebu.o
 obj-$(CONFIG_PCI_TEGRA) += pci-tegra.o
 obj-$(CONFIG_PCI_RCAR_GEN2) += pci-rcar-gen2.o
diff --git a/drivers/pci/host/hv_pcifront.c b/drivers/pci/host/hv_pcifront.c
new file mode 100644
index 0000000..14c37c2
--- /dev/null
+++ b/drivers/pci/host/hv_pcifront.c
@@ -0,0 +1,2101 @@
+/*
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Author:
+ *   Jake Oshins <jakeo@xxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/jiffies.h>
+#include <linux/mman.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/kthread.h>
+#include <linux/completion.h>
+#include <linux/notifier.h>
+#include <linux/of_pci.h>
+#include <linux/of_platform.h>
+#include <linux/pci.h>
+#include <linux/semaphore.h>
+
+#include <linux/hyperv.h>
+#include <asm/mshyperv.h>
+
+/*
+ * We begin with definitions supporting the Virtual PCI Express protocol
+ * with the host.
+ */
+
+
+/*
+ * Protocol versions. The low word is the minor version, the high word the major
+ * version.
+ */
+
+#define PCI_MAKE_VERSION(Major, Minor) ((__u32)(((Major) << 16) | (Minor)))
+#define PCI_MAJOR_VERSION(Version) ((__u32)(Version) >> 16)
+#define PCI_MINOR_VERSION(Version) ((__u32)(Version) & 0xff)
+
+enum {
+	PCI_PROTOCOL_VERSION_1_1 = PCI_MAKE_VERSION(1, 1),
+	PCI_PROTOCOL_VERSION_CURRENT = PCI_PROTOCOL_VERSION_1_1
+};
+
+#define PCI_CONFIG_MMIO_LENGTH	0x2000
+
+/*
+ * Message Types
+ */
+
+enum pci_message_type {
+	/*
+	 * Version 1.1
+	 */
+	PCI_MESSAGE_BASE                = 0x42490000,
+	PCI_BUS_RELATIONS               = PCI_MESSAGE_BASE + 0,
+	PCI_QUERY_BUS_RELATIONS         = PCI_MESSAGE_BASE + 1,
+	PCI_POWER_STATE_CHANGE          = PCI_MESSAGE_BASE + 4,
+	PCI_QUERY_RESOURCE_REQUIREMENTS = PCI_MESSAGE_BASE + 5,
+	PCI_QUERY_RESOURCE_RESOURCES    = PCI_MESSAGE_BASE + 6,
+	PCI_BUS_D0ENTRY                 = PCI_MESSAGE_BASE + 7,
+	PCI_BUS_D0EXIT                  = PCI_MESSAGE_BASE + 8,
+	PCI_READ_BLOCK                  = PCI_MESSAGE_BASE + 9,
+	PCI_WRITE_BLOCK                 = PCI_MESSAGE_BASE + 0xA,
+	PCI_EJECT                       = PCI_MESSAGE_BASE + 0xB,
+	PCI_QUERY_STOP                  = PCI_MESSAGE_BASE + 0xC,
+	PCI_REENABLE                    = PCI_MESSAGE_BASE + 0xD,
+	PCI_QUERY_STOP_FAILED           = PCI_MESSAGE_BASE + 0xE,
+	PCI_EJECTION_COMPLETE           = PCI_MESSAGE_BASE + 0xF,
+	PCI_RESOURCES_ASSIGNED          = PCI_MESSAGE_BASE + 0x10,
+	PCI_RESOURCES_RELEASED          = PCI_MESSAGE_BASE + 0x11,
+	PCI_INVALIDATE_BLOCK            = PCI_MESSAGE_BASE + 0x12,
+	PCI_QUERY_PROTOCOL_VERSION      = PCI_MESSAGE_BASE + 0x13,
+	PCI_CREATE_INTERRUPT_MESSAGE    = PCI_MESSAGE_BASE + 0x14,
+	PCI_DELETE_INTERRUPT_MESSAGE    = PCI_MESSAGE_BASE + 0x15,
+	PCI_MESSAGE_MAXIMUM
+};
+
+
+/*
+ * Structures defining the virtual PCI Express protocol.
+ */
+
+union pci_version {
+	struct {
+		__u16 minor_version;
+		__u16 major_version;
+	} parts;
+	__u32 version;
+} __packed;
+
+/*
+ * Function numbers are 8-bits wide on Express, as interpreted through ARI,
+ * which is all this driver does.
+ */
+union pci_slot_number {
+	struct {
+		__u32   func:8;
+		__u32   reserved:24;
+	} bits;
+	__u32 slot;
+} __packed;
+
+/*
+ * Pretty much as defined in the PCI Specifications.
+ */
+struct pci_function_description {
+	__u16   v_id;	/* vendor ID */
+	__u16   d_id;	/* device ID */
+	__u8    rev;
+	__u8    prog_intf;
+	__u8    subclass;
+	__u8    base_class;
+	__u32   subsystem_id;
+	union pci_slot_number s_no;
+	__u32   ser;	/* serial number */
+} __packed;
+
+/**
+ * struct hv_msi_desc
+ * @vector:		IDT entry
+ * @delivery_mode:	As defined in Intel's Programmer's
+ *  			Reference Manual, Volume 3, Chapter 8.
+ * @vector_count: 	Number of contiguous entries in the
+ *      		Interrupt Descriptor Table that are
+ *      		occupied by this Message-Signaled
+ *      		Interrupt. For "MSI", as first defined
+ *      		in PCI 2.2, this can be between 1 and
+ *      		32. For "MSI-X," as first defined in PCI
+ *      		3.0, this must be 1, as each MSI-X table
+ *      		entry would have its own descriptor.
+ * @reserved:		Empty space
+ * @cpu_mask:		All the target virtual processors.
+ */
+struct hv_msi_desc {
+	__u8	vector;
+	__u8	delivery_mode;
+	__u16	vector_count;
+	__u32	reserved;
+	__u64	cpu_mask;
+} __packed;
+
+/**
+ * struct tran_int_desc
+ * @reserved:		unused, padding
+ * @vector_count:	same as in hv_msi_desc
+ * @data: 		This is the "data payload" value that is
+ *      		written by the device when it generates
+ *      		a message-signaled interrupt, either MSI
+ *      		or MSI-X.
+ * @address:		This is the address to which the data
+ *      		payload is written on interrupt
+ *      		generation.
+ */
+struct tran_int_desc {
+	__u16	reserved;
+	__u16	vector_count;
+	__u32	data;
+	__u64	address;
+} __packed;
+
+
+/*
+ * A generic message format for virtual PCI.
+ * Specific message formats are defined later in the file.
+ */
+
+struct pci_message {
+	__u32 message_type;
+} __packed;
+
+struct pci_child_message {
+	__u32 message_type;
+	union pci_slot_number slot;
+} __packed;
+
+struct pci_incoming_message {
+	struct vmpacket_descriptor hdr;
+	struct pci_message message_type;
+} __packed;
+
+struct pci_response {
+	struct vmpacket_descriptor hdr;
+	__s32 status; /* negative values are failures*/
+} __packed;
+
+struct pci_packet {
+	void (*completion_func)(void *context, struct pci_response *resp,
+				int resp_packet_size);
+	void *compl_ctxt;
+	struct pci_message message;
+};
+
+/*
+ * Specific message types supporting the PCI protocol.
+ */
+
+/*
+ * Version negotiation message. Sent from the guest to the host.
+ * The guest is free to try different versions until the host
+ * accepts the version.
+ *
+ * pci_version: The protocol version requested.
+ * is_last_attempt: If TRUE, this is the last version guest will request.
+ * reservedz: Reserved field, set to zero.
+ */
+
+struct pci_version_request {
+	struct pci_message message_type;
+	enum pci_message_type protocol_version;
+} __packed;
+
+/*
+ * Bus D0 Entry.  This is sent from the guest to the host when the virtual
+ * bus (PCI Express port) is ready for action.
+ */
+
+struct pci_bus_d0_entry {
+	struct pci_message message_type;
+	__u32 reserved;
+	__u64 mmio_base;
+} __packed;
+
+
+struct pci_bus_relations {
+	struct pci_incoming_message incoming;
+	__u32 device_count;
+	struct pci_function_description func[1];
+} __packed;
+
+struct pci_q_res_req_response {
+	struct vmpacket_descriptor hdr;
+	__s32 status; /* negative values are failures*/
+	__u32 probed_bar[6];
+} __packed;
+
+struct pci_set_power {
+	struct pci_message message_type;
+	union pci_slot_number slot;
+	__u32 power_state; /* In Windows terms */
+	__u32 reserved;
+} __packed;
+
+
+struct pci_set_power_response {
+	struct vmpacket_descriptor hdr;
+	__s32 status; /* negative values are failures*/
+	union pci_slot_number slot;
+	__u32 resultant_state;  /* In Windows terms */
+	__u32 reserved;
+} __packed;
+
+struct pci_resources_assigned {
+	struct pci_message message_type;
+	union pci_slot_number slot;
+	u8 memory_range[0x14][6]; /* not used here */
+	u32 msi_descriptors;
+	u32 reserved[4];
+} __packed;
+
+struct pci_create_interrupt {
+	struct pci_message message_type;
+	union pci_slot_number slot;
+	struct hv_msi_desc int_desc;
+} __packed;
+
+struct pci_create_int_response {
+	struct pci_response response;
+	u32 reserved;
+	struct tran_int_desc int_desc;
+} __packed;
+
+struct pci_delete_interrupt {
+	struct pci_message message_type;
+	union pci_slot_number slot;
+	struct tran_int_desc int_desc;
+} __packed;
+
+struct pci_dev_incoming {
+	struct pci_incoming_message incoming;
+	union pci_slot_number slot;
+} __packed;
+
+struct pci_eject_response {
+	u32 message_type;
+	union pci_slot_number slot;
+	u32 status;
+} __packed;
+
+static int pci_ring_size = (4 * PAGE_SIZE);
+
+/*
+ * Driver specific state.
+ */
+
+enum hv_pcibus_state {
+	hv_pcibus_init = 0,
+	hv_pcibus_probed,
+	hv_pcibus_installed,
+	hv_pcibus_maximum
+};
+
+struct hv_pcibus_device {
+	struct pci_sysdata sysdata;
+	enum hv_pcibus_state state;
+	atomic_t remove_lock;
+	struct hv_device *hdev;
+	resource_size_t low_mmio_space;
+	resource_size_t high_mmio_space;
+	struct resource *mem_config;
+	struct resource *low_mmio_res;
+	struct resource *high_mmio_res;
+	struct completion *survey_event;
+	struct completion remove_event;
+	struct pci_bus *pci_bus;
+	spinlock_t config_lock;
+	spinlock_t device_list_lock;
+	void __iomem *cfg_addr;
+
+	struct semaphore enum_sem;
+	struct list_head resources_for_children;
+
+	/* Lists protected by device_list_lock */
+	struct list_head children;
+	struct list_head dr_list;
+	struct work_struct wrk;
+};
+
+/* Tracks "Device Relations" messages from the host, which must be both
+   processed in order and deferred so that they don't run in the context
+   of the incoming packet callback. */
+struct hv_dr_work {
+	struct work_struct wrk;
+	struct hv_pcibus_device *bus;
+};
+
+struct hv_dr_state {
+	struct list_head list_entry;
+	__u32 device_count;
+	struct pci_function_description func[1];
+};
+
+enum hv_pcichild_state {
+	hv_pcichild_init = 0,
+	hv_pcichild_requirements,
+	hv_pcichild_resourced,
+	hv_pcichild_ejecting,
+	hv_pcichild_maximum
+};
+
+enum hv_pcidev_ref_reason {
+	hv_pcidev_ref_invalid = 0,
+	hv_pcidev_ref_initial,
+	hv_pcidev_ref_by_slot,
+	hv_pcidev_ref_packet,
+	hv_pcidev_ref_pnp,
+	hv_pcidev_ref_childlist,
+	hv_pcidev_ref_max
+};
+
+static char *hv_pcidev_ref_debug[hv_pcidev_ref_max] = {
+	"hv_pcidev_ref_invalid",
+	"hv_pcidev_ref_initial",
+	"hv_pcidev_ref_by_slot",
+	"hv_pcidev_ref_packet",
+	"hv_pcidev_ref_pnp",
+	"hv_pcidev_ref_childlist"
+};
+
+struct hv_pci_dev {
+	/* List protected by pci_rescan_remove_lock */
+	struct list_head list_entry;
+	atomic_t refs;
+	enum hv_pcichild_state state;
+	/* What would be observed if one wrote 0xFFFFFFFF to a BAR and then
+	   read it back, for each of the BAR offsets within config space. */
+	u32 probed_bar[6];
+	struct pci_function_description desc;
+	bool reported_missing;
+	struct hv_pcibus_device *hbus;
+	struct work_struct wrk;
+};
+
+struct hv_pci_compl {
+	struct completion host_event;
+	__s32 completion_status;
+};
+
+struct x86_msi_ops hv_msi;
+
+/**
+ * hv_pci_generic_compl() - Invoked for a completion packet
+ * @context:		Set up by the sender of the packet.
+ * @resp:		The response packet
+ * @resp_packet_size:	Size in bytes of the packet
+ *
+ * This function is used to trigger an event and report status
+ * for any message for which the completion packet contains a
+ * status and nothing else.
+ *
+ */
+static
+void
+hv_pci_generic_compl(void *context, struct pci_response *resp,
+		     int resp_packet_size)
+{
+	struct hv_pci_compl *comp_pkt = (struct hv_pci_compl *)context;
+
+	if (resp_packet_size >= offsetofend(struct pci_response, status))
+		comp_pkt->completion_status = resp->status;
+	complete(&comp_pkt->host_event);
+}
+
+static struct hv_pci_dev *lookup_hv_pcidev(struct hv_pcibus_device *hbus,
+					   u32 slot);
+static void hv_pcichild_inc(struct hv_pci_dev *hv_pcidev,
+			    enum hv_pcidev_ref_reason reason);
+static void hv_pcichild_dec(struct hv_pci_dev *hv_pcidev,
+			    enum hv_pcidev_ref_reason reason);
+
+static void hv_pcibus_inc(struct hv_pcibus_device *hv_pcibus);
+static void hv_pcibus_dec(struct hv_pcibus_device *hv_pcibus);
+
+/**
+ * devfn_to_slot() - Convert from Linux PCI slot to Windows
+ * @devfn:	The Linux representation of PCI slot
+ *
+ * Windows uses a slightly different representation of PCI slot.
+ *
+ * Return: The Windows representation
+ */
+static u32 devfn_to_slot(int devfn)
+{
+	union pci_slot_number slot;
+
+	slot.slot = 0;
+	slot.bits.func = PCI_SLOT(devfn) | (PCI_FUNC(devfn) << 5);
+
+	return slot.slot;
+}
+
+/**
+ * slot_to_devfn() - Convert from Windows PCI slot to Linux
+ * @slot:	The Windows representation of PCI slot
+ *
+ * Windows uses a slightly different representation of PCI slot.
+ *
+ * Return: The Linux representation
+ */
+static int slot_to_devfn(u32 slot)
+{
+	union pci_slot_number slot_no;
+
+	slot_no.slot = slot;
+	return PCI_DEVFN(0, slot_no.bits.func);
+}
+
+/**
+ * _hv_pcifront_read_config() - Internal PCI config read
+ * @hpdev:	The PCI driver's representation of the device
+ * @where:	Offset within config space
+ * @size:	Size of the transfer
+ * @val:	Pointer to the buffer receiving the data
+ */
+static void _hv_pcifront_read_config(struct hv_pci_dev *hpdev, int where,
+				     int size, u32 *val)
+{
+	unsigned long flags;
+	void __iomem *addr = ((u8 *)hpdev->hbus->cfg_addr) + 0x1000 + where;
+
+	/*
+	 * If the attempt is to read the IDs or the ROM BAR, simulate that.
+	 */
+	if (where + size <= PCI_COMMAND) {
+
+		memcpy(val, ((u8 *)&(hpdev->desc.v_id)) + where, size);
+
+	} else if (where >= PCI_CLASS_REVISION && where + size <=
+		   PCI_CACHE_LINE_SIZE) {
+
+		memcpy(val, ((u8 *)&(hpdev->desc.rev)) + where -
+		       PCI_CLASS_REVISION, size);
+
+	} else if (where >= PCI_SUBSYSTEM_VENDOR_ID && where + size <=
+		   PCI_ROM_ADDRESS) {
+
+		memcpy(val, (u8 *)&hpdev->desc.subsystem_id + where -
+		       PCI_SUBSYSTEM_VENDOR_ID, size);
+
+	} else if (where >= PCI_ROM_ADDRESS && where + size <=
+		   PCI_CAPABILITY_LIST) {
+
+		/* ROM BARs are unimplemented */
+		*val = 0;
+
+	} else if (where >= PCI_INTERRUPT_LINE && where + size <=
+		   PCI_INTERRUPT_PIN) {
+
+		/*
+		 * Interrupt Line and Interrupt PIN are hard-wired to zero
+		 * because this front-end only supports message-signaled
+		 * interrupts.
+		 */
+		*val = 0;
+
+	} else {
+		spin_lock_irqsave(&hpdev->hbus->config_lock, flags);
+		writel(hpdev->desc.s_no.slot, hpdev->hbus->cfg_addr);
+		switch (size) {
+		case 1:
+			*val = readb(addr);
+			break;
+		case 2:
+			*val = readw(addr);
+			break;
+		default:
+			*val = readl(addr);
+			break;
+		}
+		spin_unlock_irqrestore(&hpdev->hbus->config_lock, flags);
+	}
+
+}
+
+/**
+ * _hv_pcifront_read_config() - Internal PCI config write
+ * @hpdev:	The PCI driver's representation of the device
+ * @where:	Offset within config space
+ * @size:	Size of the transfer
+ * @val:	The data being transferred
+ */
+static void _hv_pcifront_write_config(struct hv_pci_dev *hpdev, int where,
+				      int size, u32 val)
+{
+	unsigned long flags;
+	void __iomem *addr = ((__u8 *)hpdev->hbus->cfg_addr) + 0x1000 + where;
+
+	if (where >= PCI_SUBSYSTEM_VENDOR_ID &&
+	    where + size <= PCI_CAPABILITY_LIST) {
+
+		/* SSIDs and ROM BARs are read-only */
+
+	} else if (where >= PCI_COMMAND) {
+		spin_lock_irqsave(&hpdev->hbus->config_lock, flags);
+		writel(hpdev->desc.s_no.slot, hpdev->hbus->cfg_addr);
+		switch (size) {
+		case 1:
+			writeb(val, addr);
+			break;
+		case 2:
+			writew(val, addr);
+			break;
+		default:
+			writel(val, addr);
+			break;
+		}
+		spin_unlock_irqrestore(&hpdev->hbus->config_lock, flags);
+	}
+}
+
+/**
+ * hv_pcifront_read_config() - Read configuration space
+ * @bus: PCI Bus structure
+ * @devfn: Device/function
+ * @where: Offset from base
+ * @size: Byte/word/dword
+ * @val: Value to be read
+ *
+ * Return: PCIBIOS_SUCCESSFUL on success
+ *	   PCIBIOS_DEVICE_NOT_FOUND on failure
+ */
+static int hv_pcifront_read_config(struct pci_bus *bus, unsigned int devfn,
+				   int where, int size, u32 *val)
+{
+	struct hv_pcibus_device *hbus =
+		container_of(bus->sysdata, struct hv_pcibus_device, sysdata);
+	struct hv_pci_dev *hpdev = NULL;
+
+	hpdev = lookup_hv_pcidev(hbus, devfn_to_slot(devfn));
+	if (!hpdev)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+
+	_hv_pcifront_read_config(hpdev, where, size, val);
+
+	hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+	return PCIBIOS_SUCCESSFUL;
+}
+
+/**
+ * hv_pcifront_write_config() - Write configuration space
+ * @bus: PCI Bus structure
+ * @devfn: Device/function
+ * @where: Offset from base
+ * @size: Byte/word/dword
+ * @val: Value to be written to device
+ *
+ * Return: PCIBIOS_SUCCESSFUL on success
+ *	   PCIBIOS_DEVICE_NOT_FOUND on failure
+ */
+static int hv_pcifront_write_config(struct pci_bus *bus, unsigned int devfn,
+				    int where, int size, u32 val)
+{
+	struct hv_pcibus_device *hbus =
+	    container_of(bus->sysdata, struct hv_pcibus_device, sysdata);
+	struct hv_pci_dev *hpdev = NULL;
+
+	hpdev = lookup_hv_pcidev(hbus, devfn_to_slot(devfn));
+	if (!hpdev)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+
+	_hv_pcifront_write_config(hpdev, where, size, val);
+
+	hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+	return PCIBIOS_SUCCESSFUL;
+}
+
+/* PCIe operations */
+static struct pci_ops hv_pcifront_ops = {
+	.read  = hv_pcifront_read_config,
+	.write = hv_pcifront_write_config,
+};
+
+/* Interrupt management hooks */
+
+int hv_set_affinity(struct irq_data *data, const struct cpumask *dest,
+		    bool force)
+{
+	return 0;
+}
+
+int hv_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
+{
+	struct msi_desc *msidesc;
+	struct irq_chip *chip;
+	int ret;
+
+	/*
+	 * Call the base function which will do everything related to setting up
+	 * the tracking structures.
+	 */
+
+	ret = hv_msi.setup_msi_irqs(pdev, nvec, type);
+	if (ret)
+		return ret;
+
+	list_for_each_entry(msidesc, &pdev->msi_list, list) {
+		if (msidesc->irq) {
+			chip = irq_get_chip(msidesc->irq);
+			/*
+			 * Replace the affinity callback so that it doesn't
+			 * rearrage the message in the hardware.
+			 */
+			chip->irq_set_affinity = hv_set_affinity;
+		}
+	}
+
+	return 0;
+}
+
+struct compose_comp_ctxt {
+	struct hv_pci_compl comp_pkt;
+	struct tran_int_desc int_desc;
+};
+
+static
+void
+hv_pci_compose_compl(void *context, struct pci_response *resp,
+		     int resp_packet_size)
+{
+	struct compose_comp_ctxt *comp_pkt =
+		(struct compose_comp_ctxt *)context;
+	struct pci_create_int_response *int_resp =
+		(struct pci_create_int_response *)resp;
+
+	comp_pkt->comp_pkt.completion_status = resp->status;
+	comp_pkt->int_desc = int_resp->int_desc;
+	complete(&comp_pkt->comp_pkt.host_event);
+}
+
+/**
+ * hv_compose_msi_msg() - Supplies a valid MSI address/data
+ * @pdev:	The PCI driver's device tracking struct
+ * @irq:	The IRQ for the new MSI message
+ * @dest:	unused
+ * @msg:	Buffer that is filled in by this function
+ * @hpet_id:	unused
+ *
+ * This function unpacks the IRQ looking for target CPU set, IDT
+ * vector and mode and sends an interrupt to the parent
+ * partition asking for a mapping for that tuple in this
+ * partition.  The response supplies a data value and addres to
+ * which that data should be written to trigger that interrupt.
+ */
+void hv_compose_msi_msg(struct pci_dev *pdev, unsigned int irq,
+			unsigned int dest, struct msi_msg *msg, u8 hpet_id)
+{
+	struct irq_cfg *cfg = irq_get_chip_data(irq);
+	struct hv_pci_dev *hpdev = NULL;
+	struct pci_create_interrupt *int_pkt;
+	struct compose_comp_ctxt comp;
+	struct {
+		struct pci_packet pkt;
+		u8 buffer[sizeof(struct pci_create_interrupt) -
+			  sizeof(struct pci_message)];
+	} ctxt;
+	struct hv_pcibus_device *hbus =
+		container_of(pdev->bus->sysdata, struct hv_pcibus_device,
+			     sysdata);
+	int cpu;
+	int ret;
+
+	hpdev = lookup_hv_pcidev(hbus, devfn_to_slot(pdev->devfn));
+	if (!hpdev)
+		return;
+
+	memset(&ctxt, 0, sizeof(ctxt));
+	init_completion(&comp.comp_pkt.host_event);
+	ctxt.pkt.completion_func = hv_pci_compose_compl;
+	ctxt.pkt.compl_ctxt = &comp;
+	int_pkt = (struct pci_create_interrupt *)&ctxt.pkt.message;
+	int_pkt->message_type.message_type = PCI_CREATE_INTERRUPT_MESSAGE;
+	int_pkt->slot.slot = hpdev->desc.s_no.slot;
+	int_pkt->int_desc.vector = cfg->vector;
+	int_pkt->int_desc.vector_count = 1;
+	int_pkt->int_desc.delivery_mode =
+		(apic->irq_delivery_mode == dest_LowestPrio) ? 1 : 0;
+	for_each_cpu(cpu, cfg->domain)
+		int_pkt->int_desc.cpu_mask |=
+		(1 << vmbus_cpu_number_to_vp_number(cpu));
+
+	ret = vmbus_sendpacket(hbus->hdev->channel, int_pkt, sizeof(*int_pkt),
+			       (unsigned long)&ctxt.pkt, VM_PKT_DATA_INBAND,
+			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+	if (!ret)
+		wait_for_completion(&comp.comp_pkt.host_event);
+
+	if (comp.comp_pkt.completion_status < 0) {
+		pr_err("Request for interrupt failed: 0x%x",
+		       comp.comp_pkt.completion_status);
+		msg->address_hi = 0;
+		msg->address_lo = 0;
+		msg->data = 0;
+	} else {
+		msg->address_hi = comp.int_desc.address >> 32;
+		msg->address_lo = comp.int_desc.address & 0xffffffff;
+		msg->data = comp.int_desc.data;
+	}
+
+	hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+}
+
+/**
+ * hv_teardown_msi_irqs() - Undo hv_compose_msi_msg
+ * @pdev:	The PCI driver's device tracking struct
+ */
+void hv_teardown_msi_irqs(struct pci_dev *pdev)
+{
+	struct hv_pci_dev *hpdev = NULL;
+	struct pci_delete_interrupt *int_pkt;
+	struct msi_desc *msidesc;
+	struct {
+		struct pci_packet pkt;
+		u8 buffer[sizeof(struct pci_delete_interrupt) -
+			  sizeof(struct pci_message)];
+	} ctxt;
+	struct hv_pcibus_device *hbus =
+		container_of(pdev->bus->sysdata, struct hv_pcibus_device,
+			     sysdata);
+
+	hpdev = lookup_hv_pcidev(hbus, devfn_to_slot(pdev->devfn));
+
+	list_for_each_entry(msidesc, &pdev->msi_list, list) {
+		memset(&ctxt, 0, sizeof(ctxt));
+		int_pkt = (struct pci_delete_interrupt *)&ctxt.pkt.message;
+		int_pkt->message_type.message_type =
+			PCI_DELETE_INTERRUPT_MESSAGE;
+		int_pkt->slot.slot = hpdev->desc.s_no.slot;
+		int_pkt->int_desc.address = (u64)msidesc->msg.address_hi << 32 |
+					    msidesc->msg.address_lo;
+		int_pkt->int_desc.data = msidesc->msg.data;
+		vmbus_sendpacket(hbus->hdev->channel, int_pkt, sizeof(*int_pkt),
+				 (unsigned long)&ctxt.pkt, VM_PKT_DATA_INBAND,
+				 0);
+	}
+
+	hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+	hv_msi.teardown_msi_irqs(pdev);
+}
+
+void hv_restore_msi_irqs(struct pci_dev *pdev)
+{
+	hv_msi.restore_msi_irqs(pdev);
+}
+
+/**
+ * survey_child_resources() - Total all MMIO requirements
+ * @hbus:	Root PCI bus, as understood by this driver
+ */
+static void survey_child_resources(struct hv_pcibus_device *hbus)
+{
+	struct list_head *iter;
+	struct hv_pci_dev *hpdev;
+	resource_size_t bar_size = 0;
+	unsigned long flags;
+	struct completion *event;
+	u64 bar_val;
+	int i;
+
+	/* If nobody is waiting on the answer, don't compute it. */
+	event = xchg(&hbus->survey_event, NULL);
+	if (!event)
+		return;
+
+	/* If the answer has already been computed, go with it. */
+	if (hbus->low_mmio_space || hbus->high_mmio_space) {
+		complete(event);
+		return;
+	}
+
+	spin_lock_irqsave(&hbus->device_list_lock, flags);
+
+	/*
+	 * Due to an interesting quirk of the PCI spec, all memory regions
+	 * for a child device are a power of 2 in size and aligned in memory,
+	 * so it's sufficient to just add them up without tracking alignment.
+	 */
+	list_for_each(iter, &hbus->children) {
+		hpdev = container_of(iter, struct hv_pci_dev, list_entry);
+		for (i = 0; i < 6; i++) {
+			if (hpdev->probed_bar[i] & PCI_BASE_ADDRESS_SPACE_IO)
+				pr_err("There's an I/O BAR in this list!\n");
+
+			if (hpdev->probed_bar[i] != 0) {
+				/*
+				 * A probed BAR has all the upper bits set that
+				 * can be changed.
+				 */
+
+				bar_val = hpdev->probed_bar[i];
+				if (bar_val & PCI_BASE_ADDRESS_MEM_TYPE_64)
+					bar_val |=
+					((u64)hpdev->probed_bar[++i] << 32);
+				else
+					bar_val |= 0xffffffff00000000ULL;
+
+				bar_size = 1 +
+					~(bar_val & PCI_BASE_ADDRESS_MEM_MASK);
+
+				if (bar_val & PCI_BASE_ADDRESS_MEM_TYPE_64)
+					hbus->high_mmio_space += bar_size;
+				else
+					hbus->low_mmio_space += bar_size;
+			}
+		}
+	}
+
+	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+	complete(event);
+}
+
+/**
+ * prepopulate_bars() - Fill in BARs with defaults
+ * @hbus:	Root PCI bus, as understood by this driver
+ *
+ * The core PCI driver code seems much, much happier if the BARs
+ * for a device have values upon first scan. So fill them in.
+ * The algorithm below works down from large sizes to small,
+ * attempting to pack the assignments optimally. The assumption,
+ * enforced in other parts of the code, is that the beginning of
+ * the memory-mapped I/O space will be aligned on the largest
+ * BAR size.
+ */
+static void prepopulate_bars(struct hv_pcibus_device *hbus)
+{
+	resource_size_t high_bar_size = 0;
+	resource_size_t low_bar_size = 0;
+	resource_size_t high_base = 0;
+	resource_size_t low_base = 0;
+	resource_size_t bar_size;
+	struct hv_pci_dev *hpdev;
+	struct list_head *iter;
+	unsigned long flags;
+	u64 bar_val;
+	u32 command;
+	bool high;
+	int i;
+
+	if (hbus->low_mmio_space) {
+		low_bar_size = 1<<(63-__builtin_clzll(hbus->low_mmio_space));
+		low_base = hbus->low_mmio_res->start;
+	}
+
+	if (hbus->high_mmio_space) {
+		high_bar_size = 1<<(63-__builtin_clzll(hbus->high_mmio_space));
+		high_base = hbus->high_mmio_res->start;
+	}
+
+	spin_lock_irqsave(&hbus->device_list_lock, flags);
+
+	/* Pick addresses for the BARs. */
+	do {
+		list_for_each(iter, &hbus->children) {
+			hpdev = container_of(iter, struct hv_pci_dev,
+					     list_entry);
+
+			for (i = 0; i < 6; i++) {
+
+				bar_val = hpdev->probed_bar[i];
+				if (bar_val == 0)
+					continue;
+
+				high = bar_val & PCI_BASE_ADDRESS_MEM_TYPE_64;
+				if (high)
+					bar_val |=
+					    ((u64)hpdev->probed_bar[i+1] << 32);
+				else
+					bar_val |= 0xffffffffULL << 32;
+
+				bar_size = 1ULL +
+					~(bar_val & PCI_BASE_ADDRESS_MEM_MASK);
+
+				if (high) {
+
+					if (high_bar_size != bar_size) {
+						i++;
+						continue;
+					}
+
+					_hv_pcifront_write_config(hpdev,
+						PCI_BASE_ADDRESS_0 + (4 * i),
+						4,
+						(u32)(high_base & 0xffffff00));
+					_hv_pcifront_write_config(hpdev,
+						PCI_BASE_ADDRESS_0 +
+								  (4 * (i + 1)),
+						4, (u32)(high_base >> 32));
+
+					high_base += bar_size;
+				} else {
+					if (low_bar_size != bar_size)
+						continue;
+
+					_hv_pcifront_write_config(hpdev,
+						PCI_BASE_ADDRESS_0 + (4 * i),
+						4,
+						(u32)(low_base & 0xffffff00));
+					low_base += bar_size;
+				}
+			}
+
+			if ((high_bar_size <= 1) && (low_bar_size <= 1)) {
+				/* Set the memory enable bit. */
+				_hv_pcifront_read_config(hpdev, PCI_COMMAND, 2,
+							 &command);
+				command |= PCI_COMMAND_MEMORY;
+				_hv_pcifront_write_config(hpdev, PCI_COMMAND, 2,
+							  command);
+				break;
+			}
+		}
+
+		high_bar_size >>= 1;
+		low_bar_size >>= 1;
+	}  while (high_bar_size || low_bar_size);
+
+	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+}
+
+/**
+ * create_root_hv_pci_bus() - Expose a new root PCI bus
+ * @hbus:	Root PCI bus, as understood by this driver
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int create_root_hv_pci_bus(struct hv_pcibus_device *hbus)
+{
+	/* Register the device */
+	hbus->pci_bus = pci_create_root_bus(&hbus->hdev->device,
+					    0, /* bus number is always zero */
+					    &hv_pcifront_ops,
+					    &hbus->sysdata,
+					    &hbus->resources_for_children);
+	if (!hbus->pci_bus)
+		return -ENODEV;
+
+	pci_scan_child_bus(hbus->pci_bus);
+	pci_bus_assign_resources(hbus->pci_bus);
+	pci_bus_add_devices(hbus->pci_bus);
+	hbus->state = hv_pcibus_installed;
+	return 0;
+}
+
+struct q_res_req_compl {
+	struct completion host_event;
+	struct hv_pci_dev *hpdev;
+};
+
+/**
+ * q_resource_requirements() - Query Resource Requirements
+ * @context:		The completion context.
+ * @resp:		The respose that came from the host.
+ * @resp_packet_size:	The size in bytes of resp.
+ *
+ * This function is invoked on completion of a Query Resource
+ * Requirements packet.
+ */
+static void q_resource_requirements(void *context, struct pci_response *resp,
+				    int resp_packet_size)
+{
+	struct q_res_req_compl *completion = (struct q_res_req_compl *)context;
+	struct pci_q_res_req_response *q_res_req =
+		(struct pci_q_res_req_response *)resp;
+	int i;
+
+	if (resp->status < 0) {
+		pr_err("query resource requirements failed: %x\n",
+		       resp->status);
+	} else {
+		for (i = 0; i < 6; i++) {
+			completion->hpdev->probed_bar[i] =
+				q_res_req->probed_bar[i];
+		}
+	}
+
+	complete(&completion->host_event);
+}
+
+static void hv_pcichild_inc(struct hv_pci_dev *hpdev,
+			    enum hv_pcidev_ref_reason reason)
+{
+	pr_devel("+%s %p\n", hv_pcidev_ref_debug[reason], hpdev);
+	atomic_inc(&hpdev->refs);
+}
+
+static void hv_pcichild_dec(struct hv_pci_dev *hpdev,
+			    enum hv_pcidev_ref_reason reason)
+{
+	pr_devel("-%s %p\n", hv_pcidev_ref_debug[reason], hpdev);
+	if (atomic_dec_and_test(&hpdev->refs)) {
+		pr_devel("Freeing hv_pcidev %p\n", hpdev);
+		kfree(hpdev);
+	}
+}
+
+/**
+ * new_pcichild_device() - Create a new child device
+ * @hbus:	The internal struct tracking this root PCI bus.
+ * @desc:	The information supplied so far from the host
+ *      	about the device.
+ *
+ * This function creates the tracking structure for a new child
+ * device and kicks off the process of figuring out what it is.
+ *
+ * Return: Pointer to the new tracking struct
+ */
+static
+struct hv_pci_dev *
+new_pcichild_device(struct hv_pcibus_device *hbus,
+		    struct pci_function_description *desc)
+{
+	struct hv_pci_dev *hpdev = NULL;
+	struct pci_child_message *res_req;
+	struct q_res_req_compl comp_pkt;
+	union {
+	struct pci_packet init_packet;
+		__u8 buffer[0x100];
+	} pkt;
+	unsigned long flags;
+	int ret;
+
+	hpdev = kzalloc(sizeof(struct hv_pci_dev), GFP_ATOMIC);
+	if (!hpdev)
+		return NULL;
+
+	pr_devel("New child device (%p) reported (%04x:%04x) in slot %x.\n",
+		 hpdev, desc->v_id, desc->d_id, desc->s_no.slot);
+
+	hpdev->hbus = hbus;
+
+	memset(&pkt, 0, sizeof(pkt));
+	init_completion(&comp_pkt.host_event);
+	comp_pkt.hpdev = hpdev;
+	pkt.init_packet.compl_ctxt = &comp_pkt;
+	pkt.init_packet.completion_func = q_resource_requirements;
+	res_req = (struct pci_child_message *)&pkt.init_packet.message;
+	res_req->message_type = PCI_QUERY_RESOURCE_REQUIREMENTS;
+	res_req->slot.slot = desc->s_no.slot;
+
+	ret = vmbus_sendpacket(hbus->hdev->channel, res_req,
+			    sizeof(struct pci_child_message),
+			    (unsigned long)&pkt.init_packet,
+			    VM_PKT_DATA_INBAND,
+			    VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+	if (ret)
+		goto new_pcichild_device_error;
+
+	wait_for_completion(&comp_pkt.host_event);
+
+	hpdev->desc = *desc;
+	hv_pcichild_inc(hpdev, hv_pcidev_ref_initial);
+	hv_pcichild_inc(hpdev, hv_pcidev_ref_childlist);
+	spin_lock_irqsave(&hbus->device_list_lock, flags);
+	list_add_tail(&hpdev->list_entry, &hbus->children);
+	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+	return hpdev;
+
+new_pcichild_device_error:
+
+	kfree(hpdev);
+	return NULL;
+}
+
+/**
+ * lookup_hv_pcidev() - Find device from slot
+ * @hbus:	Root PCI bus, as understood by this driver
+ * @slot:	Location on the bus
+ *
+ * This function looks up a PCI device and returns in the
+ * internal representation of it.  It leaves a reference on it,
+ * so that the device won't be deleted while somebody is using
+ * it.  The caller is responsible for dropping this reference.
+ *
+ * Return:	Internal representation of a PCI device
+ */
+static struct hv_pci_dev *lookup_hv_pcidev(struct hv_pcibus_device *hbus,
+					   u32 slot)
+{
+	unsigned long flags;
+	struct hv_pci_dev *iter, *hpdev = NULL;
+
+	spin_lock_irqsave(&hbus->device_list_lock, flags);
+	list_for_each_entry(iter, &hbus->children, list_entry) {
+		if (iter->desc.s_no.slot == slot) {
+			hpdev = iter;
+			hv_pcichild_inc(hpdev, hv_pcidev_ref_by_slot);
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+	return hpdev;
+}
+
+/**
+ * pci_devices_present_work() - Handle new list of child devices
+ * @work:	Work struct embedded in struct hv_dr_work
+ *
+ * "Bus Relations" is the Windows term for "children of this
+ * bus."  The terminology is preserved here for people trying to
+ * debug the interaction between Hyper-V and Linux.  This
+ * function is called when the parent partition reports a list
+ * of functions that should be observed under this PCI Express
+ * port (bus).
+ *
+ * This function updates the list, and must tolerate being
+ * called multiple times with the same information.  The typical
+ * number of child devices is one, with very atypical cases
+ * involving three or four, so the algorithms used here can be
+ * simple and inefficient.
+ *
+ * It must also treat the omission of a previously observed device as
+ * notification that the device no longer exists.
+ *
+ * Note that this function is a work item, and it may not be
+ * invoked in the order that it was queued.  Back to back
+ * updates of the list of present devices may involve queuing
+ * mulitple work items, and this one may run before ones that
+ * were sent later. As such, this function only does something
+ * if is the last one in the queue.
+ */
+static void pci_devices_present_work(struct work_struct *work)
+{
+	u32 child_no;
+	bool found;
+	struct list_head *iter;
+	struct pci_function_description *new_desc;
+	struct hv_pci_dev *hpdev;
+	struct hv_pcibus_device *hbus;
+	struct list_head removed;
+	struct hv_dr_work *dr_wrk;
+	struct hv_dr_state *dr = NULL;
+	unsigned long flags;
+
+	dr_wrk = container_of(work, struct hv_dr_work, wrk);
+	hbus = dr_wrk->bus;
+
+	INIT_LIST_HEAD(&removed);
+
+	if (down_interruptible(&hbus->enum_sem))
+		return;
+
+	/* Pull this off the queue and process it if it was the last one. */
+	spin_lock_irqsave(&hbus->device_list_lock, flags);
+	while (!list_empty(&hbus->dr_list)) {
+		dr = list_first_entry(&hbus->dr_list, struct hv_dr_state,
+				      list_entry);
+		list_del(&dr->list_entry);
+
+		/* Throw this away if the list still has stuff in it. */
+		if (!list_empty(&hbus->dr_list))
+			kfree(dr);
+		}
+
+		if (dr == NULL) {
+			spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+			goto present_exit;
+		}
+
+		/* First, mark all existing children as reported missing. */
+		list_for_each(iter, &hbus->children) {
+			hpdev = container_of(iter, struct hv_pci_dev,
+					     list_entry);
+			hpdev->reported_missing = true;
+		}
+		spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+		/* Next, add back any reported devices. */
+		for (child_no = 0; child_no < dr->device_count; child_no++) {
+
+			found = false;
+			new_desc = &dr->func[child_no];
+
+			spin_lock_irqsave(&hbus->device_list_lock, flags);
+			list_for_each(iter, &hbus->children) {
+				hpdev = container_of(iter, struct hv_pci_dev,
+						     list_entry);
+
+				if ((hpdev->desc.s_no.slot ==
+				     new_desc->s_no.slot) &&
+				    (hpdev->desc.v_id == new_desc->v_id) &&
+				    (hpdev->desc.d_id == new_desc->d_id) &&
+				    (hpdev->desc.ser == new_desc->ser)) {
+					hpdev->reported_missing = false;
+					found = true;
+				}
+			}
+			spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+		if (!found) {
+
+			hpdev = new_pcichild_device(hbus, new_desc);
+			if (!hpdev) {
+				pr_err("couldn't record a child device.\n");
+				goto present_exit;
+			}
+		}
+	}
+
+	/* Move missing children to a list on the stack. */
+	spin_lock_irqsave(&hbus->device_list_lock, flags);
+	do {
+		found = false;
+		list_for_each(iter, &hbus->children) {
+			hpdev = container_of(iter, struct hv_pci_dev,
+					     list_entry);
+			if (hpdev->reported_missing) {
+				found = true;
+				hv_pcichild_dec(hpdev, hv_pcidev_ref_childlist);
+				list_del(&hpdev->list_entry);
+				list_add_tail(&hpdev->list_entry, &removed);
+				break;
+			}
+		}
+	} while (found);
+	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+present_exit:
+
+	/* Delete everything that should no longer exist. */
+	while (!list_empty(&removed)) {
+		hpdev = list_first_entry(&removed, struct hv_pci_dev,
+					 list_entry);
+		list_del(&hpdev->list_entry);
+		hv_pcichild_dec(hpdev, hv_pcidev_ref_initial);
+	}
+
+	/* Tell the core to rescan bus because there may have been changes. */
+	if (hbus->state == hv_pcibus_installed) {
+		pci_lock_rescan_remove();
+		pci_scan_child_bus(hbus->pci_bus);
+		pci_unlock_rescan_remove();
+	} else {
+		survey_child_resources(hbus);
+	}
+
+	up(&hbus->enum_sem);
+	hv_pcibus_dec(hbus);
+
+	if (dr)
+		kfree(dr);
+	kfree(dr_wrk);
+}
+
+/**
+ * hv_pci_devices_present() - Handles list of new children
+ * @hbus:	Root PCI bus, as understood by this driver
+ * @relations:	Packet from host listing children
+ *
+ * This function is invoked whenever a new list of devices for
+ * this bus appears.
+ */
+static void hv_pci_devices_present(struct hv_pcibus_device *hbus,
+				   struct pci_bus_relations *relations)
+{
+	struct hv_dr_state *dr;
+	struct hv_dr_work *dr_wrk;
+	unsigned long flags;
+
+	dr_wrk = kzalloc(sizeof(struct hv_dr_work), GFP_NOWAIT);
+
+	if (!dr_wrk)
+		goto pci_devices_present_error;
+
+	dr = kzalloc(offsetof(struct hv_dr_state, func) +
+		     (sizeof(struct pci_function_description) *
+		      (relations->device_count)), GFP_NOWAIT);
+
+	if (!dr)  {
+		kfree(dr_wrk);
+		goto pci_devices_present_error;
+	}
+
+	INIT_WORK(&dr_wrk->wrk, pci_devices_present_work);
+	dr_wrk->bus = hbus;
+	dr->device_count = relations->device_count;
+	if (dr->device_count != 0) {
+		memcpy(dr->func, relations->func,
+		       sizeof(struct pci_function_description) *
+		       dr->device_count);
+	}
+
+	spin_lock_irqsave(&hbus->device_list_lock, flags);
+	list_add_tail(&dr->list_entry, &hbus->dr_list);
+	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
+
+	hv_pcibus_inc(hbus);
+	schedule_work(&dr_wrk->wrk);
+	return;
+
+pci_devices_present_error:
+	pr_err("Couldn't allocate memory to process new device list\n");
+}
+
+/**
+ * hv_eject_device_work() - Asynchronously handles ejection
+ * @work:	Work struct embedded in internal device struct
+ *
+ * This function handles ejecting a device.  Windows will
+ * attempt to gracefully eject a device, waiting 60 seconds to
+ * hear back from the guest OS that this completed successfully.
+ * If this timer expires, the device will be forcibly removed.
+ */
+static void hv_eject_device_work(struct work_struct *work)
+{
+	struct pci_eject_response *ejct_pkt;
+	struct hv_pci_dev *hpdev;
+	struct pci_dev *pdev;
+	unsigned long flags;
+	struct {
+		struct pci_packet pkt;
+		u8 buffer[sizeof(struct pci_eject_response) -
+			  sizeof(struct pci_message)];
+	} ctxt;
+
+	hpdev = container_of(work, struct hv_pci_dev, wrk);
+
+	if (hpdev->state != hv_pcichild_ejecting) {
+		hv_pcichild_dec(hpdev, hv_pcidev_ref_pnp);
+		return;
+	}
+
+	pdev = pci_get_domain_bus_and_slot(hpdev->hbus->sysdata.domain, 0,
+					  slot_to_devfn(hpdev->desc.s_no.slot));
+	if (pdev) {
+		pci_dev_get(pdev);
+		pci_stop_and_remove_bus_device(pdev);
+		pci_dev_put(pdev);
+	}
+
+	memset(&ctxt, 0, sizeof(ctxt));
+	ejct_pkt = (struct pci_eject_response *)&ctxt.pkt.message;
+	ejct_pkt->message_type = PCI_EJECTION_COMPLETE;
+	ejct_pkt->slot.slot = hpdev->desc.s_no.slot;
+	vmbus_sendpacket(hpdev->hbus->hdev->channel, ejct_pkt,
+			 sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
+			 VM_PKT_DATA_INBAND, 0);
+
+	spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);
+	list_del(&hpdev->list_entry);
+	spin_unlock_irqrestore(&hpdev->hbus->device_list_lock, flags);
+
+	hv_pcichild_dec(hpdev, hv_pcidev_ref_childlist);
+	hv_pcichild_dec(hpdev, hv_pcidev_ref_pnp);
+	hv_pcibus_dec(hpdev->hbus);
+}
+
+/**
+ * hv_pci_eject_device() - Handles device ejection
+ * @hpdev:	Internal device tracking struct
+ *
+ * This function is invoked when an ejection packet arrives.  It
+ * just schedules work so that we don't re-enter the packet
+ * delivery code handling the ejection.
+ */
+static void hv_pci_eject_device(struct hv_pci_dev *hpdev)
+{
+	hpdev->state = hv_pcichild_ejecting;
+	hv_pcichild_inc(hpdev, hv_pcidev_ref_pnp);
+	INIT_WORK(&hpdev->wrk, hv_eject_device_work);
+	hv_pcibus_inc(hpdev->hbus);
+	schedule_work(&hpdev->wrk);
+}
+
+/**
+ * hv_pci_onchannelcallback() - Handles incoming packets
+ * @context:	Internal bus tracking struct
+ *
+ * This function is invoked whenever the host sends a packet to
+ * this channel (which is private to this root PCI bus).
+ */
+static void hv_pci_onchannelcallback(void *context)
+{
+	const int packet_size = 0x100;
+	int ret;
+	struct hv_pcibus_device *hbus = context;
+	u32 bytes_recvd;
+	u64 req_id;
+	struct vmpacket_descriptor *desc;
+	unsigned char *buffer;
+	int bufferlen = packet_size;
+	struct pci_packet *comp_packet;
+	struct pci_response *response;
+	struct pci_incoming_message *new_message;
+	struct pci_bus_relations *bus_rel;
+	struct pci_dev_incoming *dev_message;
+	struct hv_pci_dev *hpdev;
+
+	buffer = kmalloc(bufferlen, GFP_ATOMIC);
+	if (!buffer)
+		return;
+
+	do {
+	ret = vmbus_recvpacket_raw(hbus->hdev->channel, buffer, bufferlen,
+				   &bytes_recvd, &req_id);
+
+	switch (ret) {
+	case 0:
+		/*
+		 * All incoming packets must be at least as large as a
+		 * response.
+		 */
+		if (bytes_recvd <= sizeof(struct pci_response)) {
+			kfree(buffer);
+			return;
+		}
+		desc = (struct vmpacket_descriptor *)buffer;
+
+		switch (desc->type) {
+		case VM_PKT_COMP:
+
+			/*
+			 * The host is trusted, and thus its safe to interpret
+			 * this transaction ID as a pointer.
+			 */
+			comp_packet = (struct pci_packet *)req_id;
+			response = (struct pci_response *)buffer;
+			comp_packet->completion_func(comp_packet->compl_ctxt,
+						     response,
+						     bytes_recvd);
+			kfree(buffer);
+			return;
+
+		case VM_PKT_DATA_INBAND:
+
+			new_message = (struct pci_incoming_message *)buffer;
+			switch (new_message->message_type.message_type) {
+			case PCI_BUS_RELATIONS:
+
+				bus_rel = (struct pci_bus_relations *)buffer;
+				if (bytes_recvd <
+				    offsetof(struct pci_bus_relations, func) +
+				    (sizeof(struct pci_function_description) *
+				     (bus_rel->device_count))) {
+
+					pr_err("bus relations too small\n");
+					break;
+				}
+
+				hv_pci_devices_present(hbus, bus_rel);
+				break;
+
+			case PCI_EJECT:
+
+				dev_message = (struct pci_dev_incoming *)buffer;
+				hpdev = lookup_hv_pcidev(hbus,
+							dev_message->slot.slot);
+				if (hpdev) {
+					hv_pci_eject_device(hpdev);
+					hv_pcichild_dec(hpdev,
+							hv_pcidev_ref_by_slot);
+				}
+				break;
+
+			default:
+				pr_warn("Unimplemented protocol message %x\n",
+					new_message->message_type.message_type);
+				break;
+			}
+		break;
+
+		default:
+		pr_err("unhandled packet type %d, tid %llx len %d\n",
+			desc->type, req_id, bytes_recvd);
+		break;
+		}
+
+		break;
+
+	case -ENOBUFS:
+		kfree(buffer);
+		/* Handle large packet */
+		bufferlen = bytes_recvd;
+		buffer = kmalloc(bytes_recvd, GFP_ATOMIC);
+		if (!buffer)
+			return;
+
+		break;
+	}
+	} while (1);
+}
+
+/**
+ * hv_pci_protocol_negotiation() - Set up protocol
+ * @hdev:	Vmbus's tracking struct for this root PCI bus
+ *
+ * This driver is intended to support running on Windows 10
+ * (server) and later versions. It will not run on earlier
+ * versions, as they assume that many of the operations which
+ * Linux needs accomplished with a spinlock held were done via
+ * asynchronous messaging via VMBus.  Windows 10 increases the
+ * surface area of PCI emulation so that these actions can take
+ * place by suspending a virtual processor for their duration.
+ *
+ * This function negotiates the channel protocol version,
+ * failing if the host doesn't support the necessary protocol
+ * level.
+ */
+static int hv_pci_protocol_negotiation(struct hv_device *hdev)
+{
+	struct pci_version_request *version_req;
+	struct hv_pci_compl comp_pkt;
+	struct pci_packet *pkt;
+	int ret;
+
+	/*
+	 * Initiate the hand shake with the host and negotiate
+	 * a version that the host can support. We start with the
+	 * highest version number and go down if the host cannot
+	 * support it.
+	 */
+
+	pkt = kzalloc(sizeof(*pkt) + sizeof(*version_req), GFP_KERNEL);
+	if (!pkt)
+		return -ENOMEM;
+
+	init_completion(&comp_pkt.host_event);
+	pkt->completion_func = hv_pci_generic_compl;
+	pkt->compl_ctxt = &comp_pkt;
+	version_req = (struct pci_version_request *)&pkt->message;
+	version_req->message_type.message_type = PCI_QUERY_PROTOCOL_VERSION;
+	version_req->protocol_version = PCI_PROTOCOL_VERSION_CURRENT;
+
+	ret = vmbus_sendpacket(hdev->channel, version_req,
+			       sizeof(struct pci_version_request),
+			       (unsigned long)pkt, VM_PKT_DATA_INBAND,
+			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+	if (ret)
+		goto protocol_exit;
+
+	wait_for_completion(&comp_pkt.host_event);
+
+	if (comp_pkt.completion_status < 0) {
+		pr_err("PCI Pass-through VSP failed version request %x\n",
+		       comp_pkt.completion_status);
+		ret = -EPROTO;
+		goto protocol_exit;
+	}
+
+	ret = 0;
+
+protocol_exit:
+
+	kfree(pkt);
+	return ret;
+}
+
+/**
+ * hv_pci_free_bridge_windows() - Release memory regions for the
+ * bus
+ * @hbus:	Root PCI bus, as understood by this driver
+ */
+static void hv_pci_free_bridge_windows(struct hv_pcibus_device *hbus)
+{
+	if (hbus->low_mmio_space && hbus->low_mmio_res)
+		release_mem_region(hbus->low_mmio_res->start,
+				   hbus->low_mmio_res->end -
+					hbus->low_mmio_res->start + 1);
+
+	if (hbus->high_mmio_space && hbus->high_mmio_res)
+		release_mem_region(hbus->high_mmio_res->start,
+				   hbus->high_mmio_res->end -
+					hbus->high_mmio_res->start + 1);
+}
+
+/**
+ * hv_pci_allocate_bridge_windows() - Allocate memory regions
+ * for the bus
+ * @hbus:	Root PCI bus, as understood by this driver
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int hv_pci_allocate_bridge_windows(struct hv_pcibus_device *hbus)
+{
+	resource_size_t align;
+	int ret;
+
+	if (hbus->low_mmio_space) {
+		align = 1 << (63-__builtin_clzll(hbus->low_mmio_space));
+		ret = vmbus_allocate_mmio(&hbus->low_mmio_res, hbus->hdev, 0,
+					  (u64)(u32)0xffffffff,
+					  hbus->low_mmio_space,
+					  align, false);
+		if (ret)
+			return ret;
+
+		hbus->low_mmio_res->flags |= IORESOURCE_WINDOW;
+		hbus->low_mmio_res->flags &= ~IORESOURCE_BUSY;
+		pci_add_resource(&hbus->resources_for_children,
+				 hbus->low_mmio_res);
+	}
+
+
+	if (hbus->high_mmio_space) {
+		align = 1 << (63-__builtin_clzll(hbus->high_mmio_space));
+		ret = vmbus_allocate_mmio(&hbus->high_mmio_res, hbus->hdev,
+					  0x100000000, -1,
+					  hbus->high_mmio_space, align,
+					  false);
+		if (ret)
+			goto release;
+
+		hbus->high_mmio_res->flags |= IORESOURCE_WINDOW;
+		hbus->high_mmio_res->flags &= ~IORESOURCE_BUSY;
+		pci_add_resource(&hbus->resources_for_children,
+				 hbus->high_mmio_res);
+	}
+
+	return 0;
+
+release:
+
+	hv_pci_free_bridge_windows(hbus);
+	return ret;
+}
+
+/**
+ * hv_pci_d0_entry() - Bring the "bus" into the D0 power state
+ * @hdev:	Vmbus's tracking struct for this root PCI bus
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int hv_pci_d0_entry(struct hv_device *hdev)
+{
+	struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
+	struct pci_bus_d0_entry *d0_entry;
+	struct hv_pci_compl comp_pkt;
+	struct pci_packet *pkt;
+	int ret;
+
+	/*
+	 * Tell the host that the bus is ready to use, and moved into the
+	 * powered-on state.  This includes telling the host which region
+	 * of memory-mapped I/O space has been chosen for configuration space
+	 * access.
+	 */
+
+	pkt = kzalloc(sizeof(*pkt) + sizeof(*d0_entry), GFP_KERNEL);
+	if (!pkt)
+		return -ENOMEM;
+
+	init_completion(&comp_pkt.host_event);
+	pkt->completion_func = hv_pci_generic_compl;
+	pkt->compl_ctxt = &comp_pkt;
+	d0_entry = (struct pci_bus_d0_entry *)&pkt->message;
+	d0_entry->message_type.message_type = PCI_BUS_D0ENTRY;
+	d0_entry->mmio_base = hbus->mem_config->start;
+
+	ret = vmbus_sendpacket(hdev->channel, d0_entry, sizeof(*d0_entry),
+			       (unsigned long)pkt, VM_PKT_DATA_INBAND,
+			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+	if (ret)
+		goto d0_entry_exit;
+	wait_for_completion(&comp_pkt.host_event);
+
+	if (comp_pkt.completion_status < 0) {
+		pr_err("PCI Pass-through VSP failed D0 Entry with status %x\n",
+		       comp_pkt.completion_status);
+		ret = -EPROTO;
+		goto d0_entry_exit;
+	}
+
+	ret = 0;
+
+d0_entry_exit:
+
+	kfree(pkt);
+	return ret;
+}
+
+/**
+ * hv_pci_query_relations() - Ask host to send list of child
+ * devices
+ * @hdev:	Vmbus's tracking struct for this root PCI bus
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int hv_pci_query_relations(struct hv_device *hdev)
+{
+	struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
+	struct pci_message message;
+	struct completion comp;
+	int ret;
+
+	/*
+	 * Ask the host to send along the list of child devices.
+	 */
+
+	init_completion(&comp);
+	if (!cmpxchg(&hbus->survey_event, NULL, &comp)) {
+		memset(&message, 0, sizeof(message));
+		message.message_type = PCI_QUERY_BUS_RELATIONS;
+
+		ret = vmbus_sendpacket(hdev->channel, &message, sizeof(message),
+				       0, VM_PKT_DATA_INBAND, 0);
+		if (ret)
+			return ret;
+
+		wait_for_completion(&comp);
+		return 0;
+	} else
+		return -ENOTEMPTY;
+}
+
+/**
+ * hv_send_resources_allocated() - Report local resource choices
+ * @hdev:	Vmbus's tracking struct for this root PCI bus
+ *
+ * The host OS is expecting to be sent a request as a message
+ * which contains all the resources that the device will use.
+ * The response contains those same resources, "translated"
+ * which is to say, the values which should be used by the
+ * hardware, when it delivers an interrupt.  (MMIO resources are
+ * used in local terms.)  This is nice for Windows, and lines up
+ * with the FDO/PDO split, which doesn't exist in Linux.  Linux
+ * is deeply expecting to scan an emulated PCI configuration
+ * space.  So this message is sent here only to drive the state
+ * machine on the host forward.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int hv_send_resources_allocated(struct hv_device *hdev)
+{
+	struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
+	struct pci_resources_assigned *res_assigned;
+	struct hv_pci_compl comp_pkt;
+	struct hv_pci_dev *hpdev;
+	struct pci_packet *pkt;
+	u32 slot;
+	int ret;
+
+	pkt = kmalloc(sizeof(*pkt) + sizeof(*res_assigned), GFP_KERNEL);
+	if (!pkt)
+		return -ENOMEM;
+
+	for (slot = 0; slot < 256; slot++) {
+		hpdev = lookup_hv_pcidev(hbus, slot);
+		if (hpdev) {
+			memset(pkt, 0, sizeof(*pkt) + sizeof(*res_assigned));
+			init_completion(&comp_pkt.host_event);
+			pkt->completion_func = hv_pci_generic_compl;
+			pkt->compl_ctxt = &comp_pkt;
+			pkt->message.message_type = PCI_RESOURCES_ASSIGNED;
+			res_assigned =
+				(struct pci_resources_assigned *)&pkt->message;
+			res_assigned->slot.slot = hpdev->desc.s_no.slot;
+
+			hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+
+			ret = vmbus_sendpacket(
+				hdev->channel, &pkt->message,
+				sizeof(*res_assigned),
+				(unsigned long)pkt,
+				VM_PKT_DATA_INBAND,
+				VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+			if (ret)
+				goto send_resources_allocated_free;
+
+			wait_for_completion(&comp_pkt.host_event);
+
+			if (comp_pkt.completion_status < 0) {
+				ret = -EPROTO;
+				pr_err("resource allocated returned 0x%x",
+				       comp_pkt.completion_status);
+				goto send_resources_allocated_free;
+			}
+		}
+	}
+	ret = 0;
+
+send_resources_allocated_free:
+
+	kfree(pkt);
+	return ret;
+}
+
+/**
+ * hv_send_resources_released() - Report local resources
+ * released
+ * @hdev:	Vmbus's tracking struct for this root PCI bus
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int hv_send_resources_released(struct hv_device *hdev)
+{
+	struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
+	struct pci_child_message pkt;
+	struct hv_pci_dev *hpdev;
+	u32 slot;
+	int ret;
+
+	for (slot = 0; slot < 256; slot++) {
+		hpdev = lookup_hv_pcidev(hbus, slot);
+		if (hpdev) {
+			memset(&pkt, 0, sizeof(pkt));
+			pkt.message_type = PCI_RESOURCES_RELEASED;
+			pkt.slot.slot = hpdev->desc.s_no.slot;
+
+			hv_pcichild_dec(hpdev, hv_pcidev_ref_by_slot);
+
+			ret = vmbus_sendpacket(hdev->channel, &pkt,
+					       sizeof(pkt), 0,
+					       VM_PKT_DATA_INBAND, 0);
+			if (ret)
+				return ret;
+		}
+	}
+
+	return 0;
+}
+
+static void hv_pcibus_inc(struct hv_pcibus_device *hbus)
+{
+	atomic_inc(&hbus->remove_lock);
+}
+
+static void hv_pcibus_dec(struct hv_pcibus_device *hbus)
+{
+	if (atomic_dec_and_test(&hbus->remove_lock))
+		complete(&hbus->remove_event);
+}
+
+/**
+ * hv_pci_probe() - New VMBus channel probe, for a root PCI bus
+ * @hdev:	Vmbus's tracking struct for this root PCI bus
+ * @dev_id:	Indentifies the device itself
+  *
+ * Return: 0 on success, -errno on failure
+ */
+static int hv_pci_probe(struct hv_device *hdev,
+			const struct hv_vmbus_device_id *dev_id)
+{
+	struct hv_pcibus_device *hbus;
+	int ret;
+
+	hbus = devm_kzalloc(&hdev->device, sizeof(*hbus), GFP_KERNEL);
+	if (!hbus)
+		return -ENOMEM;
+
+	pr_devel("New virtual PCIe bus: %p\n", hbus);
+
+	hbus->hdev = hdev;
+	INIT_LIST_HEAD(&hbus->children);
+	INIT_LIST_HEAD(&hbus->dr_list);
+	INIT_LIST_HEAD(&hbus->resources_for_children);
+	spin_lock_init(&hbus->config_lock);
+	spin_lock_init(&hbus->device_list_lock);
+	sema_init(&hbus->enum_sem, 1);
+	init_completion(&hbus->remove_event);
+	hv_pcibus_inc(hbus);
+
+	/*
+	 * The PCI bus "domain" is what is called "segment" in the
+	 * ACPI and other specs.  Pull it from the instance ID,
+	 * to get something unique.  Bytes 8 and 9 are what is used
+	 * in Windows guests, so do the same thing for consistency.
+	 */
+
+	hbus->sysdata.domain = hdev->dev_instance.b[9] |
+			       hdev->dev_instance.b[8] << 8;
+
+	ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
+			 hv_pci_onchannelcallback, hbus);
+	if (ret)
+		return ret;
+
+	hv_set_drvdata(hdev, hbus);
+
+	ret = hv_pci_protocol_negotiation(hdev);
+	if (ret)
+		goto probe_close;
+
+	/*
+	 * Set up a region of MMIO space to use for accessing configuration
+	 * space.
+	 */
+	ret = vmbus_allocate_mmio(&hbus->mem_config, hdev, 0, -1,
+				  PCI_CONFIG_MMIO_LENGTH, 0x1000, false);
+	if (ret)
+		goto probe_close;
+
+	hbus->mem_config->flags |= IORESOURCE_BUSY;
+	hbus->cfg_addr = ioremap(hbus->mem_config->start,
+				 PCI_CONFIG_MMIO_LENGTH);
+	if (!hbus->cfg_addr) {
+		pr_err("Unable to map a virtual address for config space\n");
+		ret = -ENOMEM;
+		goto probe_release;
+	}
+
+	ret = hv_pci_query_relations(hdev);
+	if (ret)
+		goto probe_unmap;
+
+	ret = hv_pci_d0_entry(hdev);
+	if (ret)
+		goto probe_unmap;
+
+	ret = hv_pci_allocate_bridge_windows(hbus);
+	if (ret)
+		goto probe_unmap;
+
+	ret = hv_send_resources_allocated(hdev);
+	if (ret)
+		goto probe_unmap;
+
+	prepopulate_bars(hbus);
+
+	hbus->state = hv_pcibus_probed;
+
+	ret = create_root_hv_pci_bus(hbus);
+	if (ret)
+		goto probe_free_windows;
+	return 0;
+
+probe_free_windows:
+	hv_pci_free_bridge_windows(hbus);
+probe_unmap:
+	iounmap(hbus->cfg_addr);
+probe_release:
+	release_mem_region(hbus->mem_config->start, PCI_CONFIG_MMIO_LENGTH);
+probe_close:
+	vmbus_close(hdev->channel);
+	return ret;
+}
+
+/**
+ * hv_pci_remove() - Remove routine for this VMBus channel
+ * @hdev:	Vmbus's tracking struct for this root PCI bus
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int hv_pci_remove(struct hv_device *hdev)
+{
+	int ret;
+	struct hv_pcibus_device *hbus;
+	union {
+	struct pci_packet teardown_packet;
+		__u8 buffer[0x100];
+	} pkt;
+	struct pci_bus_relations relations;
+	struct hv_pci_compl comp_pkt;
+
+	hbus = hv_get_drvdata(hdev);
+
+	ret = hv_send_resources_released(hdev);
+	if (ret)
+		pr_err("Couldn't send resources released packet(s)\n");
+
+	memset(&pkt.teardown_packet, 0, sizeof(pkt.teardown_packet));
+	init_completion(&comp_pkt.host_event);
+	pkt.teardown_packet.completion_func = hv_pci_generic_compl;
+	pkt.teardown_packet.compl_ctxt = &comp_pkt;
+	pkt.teardown_packet.message.message_type = PCI_BUS_D0EXIT;
+
+	ret = vmbus_sendpacket(hdev->channel, &pkt.teardown_packet.message,
+			       sizeof(struct pci_message),
+			       (unsigned long)&pkt.teardown_packet,
+			       VM_PKT_DATA_INBAND,
+			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+	if (!ret)
+		wait_for_completion_timeout(&comp_pkt.host_event, 5*HZ);
+
+	if (hbus->state == hv_pcibus_installed) {
+		/* Remove the bus from PCI's point of view. */
+		pci_lock_rescan_remove();
+		pci_stop_root_bus(hbus->pci_bus);
+		pci_remove_root_bus(hbus->pci_bus);
+		pci_unlock_rescan_remove();
+	}
+
+	vmbus_close(hdev->channel);
+
+	/* Delete any children which might still exist. */
+	memset(&relations, 0, sizeof(relations));
+	hv_pci_devices_present(hbus, &relations);
+
+	iounmap(hbus->cfg_addr);
+	release_mem_region(hbus->mem_config->start, PCI_CONFIG_MMIO_LENGTH);
+	hv_pci_free_bridge_windows(hbus);
+	pci_free_resource_list(&hbus->resources_for_children);
+	hv_pcibus_dec(hbus);
+	wait_for_completion(&hbus->remove_event);
+	return 0;
+}
+
+static const struct hv_vmbus_device_id hv_pci_id_table[] = {
+	/* PCI Pass-through Class ID */
+	/* 44C4F61D-4444-4400-9D52-802E27EDE19F */
+	{ HV_PCIE_GUID, },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(vmbus, hv_pci_id_table);
+
+static  struct hv_driver hv_pci_drv = {
+	.name = "hv_pci",
+	.id_table = hv_pci_id_table,
+	.probe = hv_pci_probe,
+	.remove =  hv_pci_remove,
+};
+
+static void exit_hv_pci_drv(void)
+{
+	vmbus_driver_unregister(&hv_pci_drv);
+	hyperv_uninstall_interrupt_translation();
+}
+
+static int __init init_hv_pci_drv(void)
+{
+	int ret;
+
+	hv_msi.setup_msi_irqs = hv_setup_msi_irqs;
+	hv_msi.compose_msi_msg = hv_compose_msi_msg;
+	hv_msi.teardown_msi_irqs = hv_teardown_msi_irqs;
+	hv_msi.restore_msi_irqs = hv_restore_msi_irqs;
+
+	/*
+	 * Hook the MSI management functions so that interrupts can be
+	 * remapped through the hypervisor.
+	 */
+
+	hyperv_install_interrupt_translation(&hv_msi);
+
+	/* Register this driver with VMBus. */
+	ret = vmbus_driver_register(&hv_pci_drv);
+
+	if (ret < 0)
+		exit_hv_pci_drv();
+
+	return ret;
+}
+
+module_init(init_hv_pci_drv);
+module_exit(exit_hv_pci_drv);
+
+MODULE_DESCRIPTION("Hyper-V PCI");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1

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