[PATCH 1/2] Drivers: hv: vmbus: add support to ignore certain PCIE devices

[longli]

From: Long Li <longli@xxxxxxxxxxxxx>

When Hyper-v presents a FlexIOV device to VMBUS, this device has its VMBUS
channel and a PCIE channel. The PCIE channel is not used in Linux and does
not have a backing PCIE device on Hyper-v. For such FlexIOV devices, add
the code to ignore those PCIE devices so they are not getting probed by the
PCI subsystem.

Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu@xxxxxxxxxx>
Cc: Dexuan Cui <decui@xxxxxxxxxxxxx>
Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
---
 drivers/hv/channel_mgmt.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index caf6d0c..6fd7ae5 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -26,6 +26,20 @@
 
 static void init_vp_index(struct vmbus_channel *channel);
 
+/*
+ * Hyper-v presents FlexIOV devices on the PCIE.
+ * Those devices have no real PCI implementation in Hyper-V, and should be
+ * ignored and not presented to the PCI layer.
+ */
+static const guid_t vpci_ignore_instances[] = {
+	/*
+	 * XStore Fastpath instance ID in VPCI introduced by FlexIOV
+	 * {d4573da2-2caa-4711-a8f9-bbabf4ee9685}
+	 */
+	GUID_INIT(0xd4573da2, 0x2caa, 0x4711, 0xa8, 0xf9,
+		0xbb, 0xab, 0xf4, 0xee, 0x96, 0x85),
+};
+
 const struct vmbus_device vmbus_devs[] = {
 	/* IDE */
 	{ .dev_type = HV_IDE,
@@ -487,6 +501,16 @@ void vmbus_free_channels(void)
 	}
 }
 
+static bool ignore_pcie_device(guid_t *if_instance)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(vpci_ignore_instances); i++)
+		if (guid_equal(&vpci_ignore_instances[i], if_instance))
+			return true;
+	return false;
+}
+
 /* Note: the function can run concurrently for primary/sub channels. */
 static void vmbus_add_channel_work(struct work_struct *work)
 {
@@ -958,6 +982,17 @@ static bool vmbus_is_valid_device(const guid_t *guid)
 	return false;
 }
 
+static bool is_pcie_offer(struct vmbus_channel_offer_channel *offer)
+{
+	int i;
+
+	for (i = HV_IDE; i < HV_UNKNOWN; i++)
+		if (guid_equal(&offer->offer.if_type, &vmbus_devs[i].guid))
+			break;
+
+	return i == HV_PCIE;
+}
+
 /*
  * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
  *
@@ -1051,6 +1086,14 @@ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 		return;
 	}
 
+	/* Check to see if we should ignore this PCIe channel */
+	if (is_pcie_offer(offer) &&
+	    ignore_pcie_device(&offer->offer.if_instance)) {
+		pr_info("Ignore instance %pUl over VPCI\n",
+			&offer->offer.if_instance);
+		return;
+	}
+
 	/* Allocate the channel object and save this offer. */
 	newchannel = alloc_channel();
 	if (!newchannel) {
-- 
1.8.3.1