RE: [EXTERNAL] [PATCH RFC 2/2] PCI: hv: Add vPCI device reset support

[Long Li]

> -----Original Message-----
> From: wei.liu@xxxxxxxxxx <wei.liu@xxxxxxxxxx>
> Sent: Friday, July 24, 2026 4:09 PM
> To: Linux on Hyper-V List <linux-hyperv@xxxxxxxxxxxxxxx>; linux-
> pci@xxxxxxxxxxxxxxx
> Cc: Wei Liu <wei.liu@xxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>;
> Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Dexuan Cui
> <DECUI@xxxxxxxxxxxxx>; Long Li <longli@xxxxxxxxxxxxx>; Jonathan Corbet
> <corbet@xxxxxxx>; Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>; Lorenzo
> Pieralisi <lpieralisi@xxxxxxxxxx>; Krzysztof Wilczyński
> <kwilczynski@xxxxxxxxxx>; Manivannan Sadhasivam <mani@xxxxxxxxxx>; Rob
> Herring <robh@xxxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; open
> list:DOCUMENTATION <linux-doc@xxxxxxxxxxxxxxx>; open list <linux-
> kernel@xxxxxxxxxxxxxxx>
> Subject: [EXTERNAL] [PATCH RFC 2/2] PCI: hv: Add vPCI device reset support
> 
> From: Wei Liu <wei.liu@xxxxxxxxxx>
> 
> Hyper-V vPCI protocol version 1.5 adds a RESET_DEVICE request for projected
> PCI functions. Negotiate the new protocol version and issue the request
> through the vPCI VMBus channel from the PCI controller reset callback.
> 
> Use the existing VMBus response path. Return -ENOTTY when the host
> reports STATUS_NOT_SUPPORTED so PCI core may try another reset method.
> 
> Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>

Reviewed-by: Long Li <longli@xxxxxxxxxxxxx>





> ---
>  Documentation/virt/hyperv/vpci.rst  |  2 +-  drivers/pci/controller/pci-
> hyperv.c | 61 +++++++++++++++++++++++++++++
>  2 files changed, 62 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/virt/hyperv/vpci.rst
> b/Documentation/virt/hyperv/vpci.rst
> index b65b2126ede3..6bfee7225c14 100644
> --- a/Documentation/virt/hyperv/vpci.rst
> +++ b/Documentation/virt/hyperv/vpci.rst
> @@ -65,7 +65,7 @@ exchange messages with the vPCI VSP for the purpose
> of setting  up and configuring the vPCI device in Linux.  Once the device  is
> fully configured in Linux as a PCI device, the VMBus  channel is used only if
> Linux changes the vCPU to be interrupted -in the guest, or if the vPCI device
> is removed from
> +in the guest, or if the vPCI device is reset or removed from
>  the VM while the VM is running.  The ongoing operation of the  device
> happens directly between the Linux device driver for  the device and the
> hardware, with VMBus and the VMBus channel diff --git
> a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index cfc8fa403dad..d3c0fd5e1d8e 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -68,6 +68,7 @@ enum pci_protocol_version_t {
>  	PCI_PROTOCOL_VERSION_1_2 = PCI_MAKE_VERSION(1, 2),	/*
> RS1 */
>  	PCI_PROTOCOL_VERSION_1_3 = PCI_MAKE_VERSION(1, 3),	/*
> Vibranium */
>  	PCI_PROTOCOL_VERSION_1_4 = PCI_MAKE_VERSION(1, 4),	/*
> WS2022 */
> +	PCI_PROTOCOL_VERSION_1_5 = PCI_MAKE_VERSION(1, 5),	/* GE,
> device reset */
>  };
> 
>  #define CPU_AFFINITY_ALL	-1ULL
> @@ -77,6 +78,7 @@ enum pci_protocol_version_t {
>   * first.
>   */
>  static enum pci_protocol_version_t pci_protocol_versions[] = {
> +	PCI_PROTOCOL_VERSION_1_5,
>  	PCI_PROTOCOL_VERSION_1_4,
>  	PCI_PROTOCOL_VERSION_1_3,
>  	PCI_PROTOCOL_VERSION_1_2,
> @@ -90,6 +92,7 @@ static enum pci_protocol_version_t
> pci_protocol_versions[] = {  #define MAX_SUPPORTED_MSI_MESSAGES 0x400
> 
>  #define STATUS_REVISION_MISMATCH 0xC0000059
> +#define STATUS_NOT_SUPPORTED     0xC00000BB
> 
>  /* space for 32bit serial number as string */  #define SLOT_NAME_SIZE 11
> @@ -136,6 +139,7 @@ enum pci_message_type {
>  	PCI_BUS_RELATIONS2		= PCI_MESSAGE_BASE + 0x19,
>  	PCI_RESOURCES_ASSIGNED3         = PCI_MESSAGE_BASE + 0x1A,
>  	PCI_CREATE_INTERRUPT_MESSAGE3   = PCI_MESSAGE_BASE + 0x1B,
> +	PCI_RESET_DEVICE                = PCI_MESSAGE_BASE + 0x1C,
>  	PCI_MESSAGE_MAXIMUM
>  };
> 
> @@ -1397,10 +1401,66 @@ static int hv_pcifront_write_config(struct pci_bus
> *bus, unsigned int devfn,
>  	return PCIBIOS_SUCCESSFUL;
>  }
> 
> +static int hv_pcifront_reset(struct pci_dev *pdev, bool probe) {
> +	struct hv_pcibus_device *hbus =
> +		container_of(pdev->bus->sysdata, struct hv_pcibus_device,
> sysdata);
> +	struct pci_child_message reset = {};
> +	struct hv_pci_compl comp_pkt;
> +	struct pci_packet pkt = {
> +		.completion_func = hv_pci_generic_compl,
> +		.compl_ctxt = &comp_pkt,
> +	};
> +	enum hv_pcibus_state state;
> +	int ret;
> +
> +	/* Device reset was added in vPCI protocol version 1.5. */
> +	if (hbus->protocol_version < PCI_PROTOCOL_VERSION_1_5)
> +		return -ENOTTY;
> +
> +	/* Hyper-V exposes projected functions directly on the root bus. */
> +	if (!pci_is_root_bus(pdev->bus))
> +		return -ENOTTY;
> +
> +	if (probe)
> +		return 0;
> +
> +	/* Do not take state_lock: eject holds it while removing/locking pdev.
> */
> +	state = READ_ONCE(hbus->state);
> +	if (state != hv_pcibus_probed && state != hv_pcibus_installed)
> +		return -ENODEV;
> +
> +	init_completion(&comp_pkt.host_event);
> +	reset.message_type.type = PCI_RESET_DEVICE;
> +	reset.wslot.slot = devfn_to_wslot(pdev->devfn);
> +
> +	ret = vmbus_sendpacket(hbus->hdev->channel, &reset, sizeof(reset),
> +			       (unsigned long)&pkt, VM_PKT_DATA_INBAND,
> +
> VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> +	if (ret)
> +		return ret;
> +
> +	ret = wait_for_response(hbus->hdev, &comp_pkt.host_event);
> +	if (ret)
> +		return ret;
> +
> +	if (comp_pkt.completion_status == STATUS_NOT_SUPPORTED)
> +		return -ENOTTY;
> +
> +	if (comp_pkt.completion_status) {
> +		pci_err(pdev, "Hyper-V device reset failed: %#x\n",
> +			comp_pkt.completion_status);
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}
> +
>  /* PCIe operations */
>  static struct pci_ops hv_pcifront_ops = {
>  	.read  = hv_pcifront_read_config,
>  	.write = hv_pcifront_write_config,
> +	.reset = hv_pcifront_reset,
>  };
> 
>  /*
> @@ -1996,6 +2056,7 @@ static void hv_compose_msi_msg(struct irq_data
> *data, struct msi_msg *msg)
>  		break;
> 
>  	case PCI_PROTOCOL_VERSION_1_4:
> +	case PCI_PROTOCOL_VERSION_1_5:
>  		size = hv_compose_msi_req_v3(&ctxt.int_pkts.v3,
>  					cpu,
>  					hpdev->desc.win_slot.slot,
> --
> 2.53.0