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PCI: hv: Use bytes 4 and 5 from instance ID as the PCI domain numbers

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As recommended by Azure host team, the bytes 4, 5 have more uniqueness
(info entropy) than bytes 8, 9 so use them as the PCI domain numbers.

On older hosts, bytes 4, 5 can also be used -- no backward compatibility
issues are introduced and 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>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Haiyang Zhang 2019-08-15 17:01:45 +00:00 committed by Lorenzo Pieralisi
parent be700103ef
commit f73f8a504e
1 changed files with 1 additions and 1 deletions
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2
drivers/pci/controller/pci-hyperv.c
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@ -2590,7 +2590,7 @@ static int hv_pci_probe(struct hv_device *hdev,
* (2) There will be no overlap between domains (after fixing possible * (2) There will be no overlap between domains (after fixing possible
* collisions) in the same VM. * 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); dom = hv_get_dom_num(dom_req);
if (dom == HVPCI_DOM_INVALID) { if (dom == HVPCI_DOM_INVALID) {