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[v6,2/2] PCI: hv: Use bytes 4 and 5 from instance ID as the PCI domain numbers

Message ID 1565888460-38694-2-git-send-email-haiyangz@microsoft.com (mailing list archive)
State Mainlined, archived
Commit f73f8a504e27959576a2f4d85182202561e426f2
Headers show
Series [v6,1/2] PCI: hv: Detect and fix Hyper-V PCI domain number collision | expand

Commit Message

Haiyang Zhang Aug. 15, 2019, 5:01 p.m. UTC 
As recommended by Azure host team, the bytes 4, 5 have more uniqueness
(info entropy) than bytes 8, 9. So now we use bytes 4, 5 as the PCI domain
numbers. On older hosts, bytes 4, 5 can also be used -- no backward
compatibility issues here. The chance of collision is greatly reduced.

In the rare cases of collision, the driver code detects and finds another
number that is not in use.

Suggested-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Acked-by: Sasha Levin <sashal@kernel.org>
---
 drivers/pci/controller/pci-hyperv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 31b8fd5..4f3d97e 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2590,7 +2590,7 @@  static int hv_pci_probe(struct hv_device *hdev,
 	 * (2) There will be no overlap between domains (after fixing possible
 	 * collisions) in the same VM.
 	 */
-	dom_req = hdev->dev_instance.b[8] << 8 | hdev->dev_instance.b[9];
+	dom_req = hdev->dev_instance.b[5] << 8 | hdev->dev_instance.b[4];
 	dom = hv_get_dom_num(dom_req);
 
 	if (dom == HVPCI_DOM_INVALID) {