From: Haiyang Zhang <haiyangz@microsoft.com>
To: "sashal@kernel.org" <sashal@kernel.org>,
"bhelgaas@google.com" <bhelgaas@google.com>,
"lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>,
KY Srinivasan <kys@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
"olaf@aepfle.de" <olaf@aepfle.de>, vkuznets <vkuznets@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH v4,2/2] PCI: hv: Use bytes 4 and 5 from instance ID as the PCI domain numbers
Date: Wed, 14 Aug 2019 00:39:35 +0000 [thread overview]
Message-ID: <1565743084-2069-2-git-send-email-haiyangz@microsoft.com> (raw)
In-Reply-To: <1565743084-2069-1-git-send-email-haiyangz@microsoft.com>
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 --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) {
--
1.8.3.1
next prev parent reply other threads:[~2019-08-14 0:39 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 0:38 [PATCH v4,1/2] PCI: hv: Detect and fix Hyper-V PCI domain number collision Haiyang Zhang
2019-08-14 0:39 ` Haiyang Zhang [this message]
2019-08-14 4:34 ` Bjorn Helgaas
2019-08-14 15:32 ` Haiyang Zhang
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