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[eoan:linux-azure,4/4] PCI: hv: Use bytes 4 and 5 from instance ID as the PCI domain numbers

Message ID 20200426204627.121419-5-marcelo.cerri@canonical.com
State New
Headers show
Series LP:#1867220 - Assignment of VDEV Somtimes Fails using Intel QAT | expand

Commit Message

Marcelo Henrique Cerri April 26, 2020, 8:46 p.m. UTC 
From: Haiyang Zhang <haiyangz@microsoft.com>

BugLink: https://bugs.launchpad.net/bugs/1867220

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>
(cherry picked from commit f73f8a504e27959576a2f4d85182202561e426f2)
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
---
 drivers/pci/controller/pci-hyperv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 4caa3388692a..3a56de6b2ec2 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) {