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SubjectRe: [PATCH v5] PCI: hv: Make sure the bus domain is really unique
  >When Linux runs as a guest VM in Hyper-V and Hyper-V adds the virtual
>PCI bus to the guest, Hyper-V always provides unique PCI domain.
>commit 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI domain")
>overrode unique domain with the serial number of the first device added
>to the virtual PCI bus. The reason for that patch is to have a consistent
>and short name for the device. But commit 4a9b0933bdfc ("PCI: hv: Use
>device serial number as PCI domain") will not guarantee unique domain id.
>For example, if the serial number of the device is 0 and there exists a
>PCI bus with domain 0 already, this will cause the PCI bus registration
>with kernel fails.
>commit 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI
>domain") need to be reverted. Also, we no longer need it as commit
>4a1626dd233e ("netvsc: transparent VF management") remove the
>need for it.
>Revert commit 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI
>domain") so we can reliably support multiple devices being assigned to
>a guest.
>This revert should only be backported to kernels that contain commit
>4a1626dd233e ("netvsc: transparent VF management").
>Fixes: 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI domain")
>Signed-off-by: Sridhar Pitchai <>
>Changes in v5:
>* fix the commit comment. [Lorenzo Pieralisi, Bjorn Helgaas]
>* fixed the patch white space.
> drivers/pci/host/pci-hyperv.c | 11 -----------
> 1 file changed, 11 deletions(-)
>diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
>index 2faf38eab785..ac67e56e451a 100644
>--- a/drivers/pci/host/pci-hyperv.c
>+++ b/drivers/pci/host/pci-hyperv.c
>@@ -1518,17 +1518,6 @@ static struct hv_pci_dev *new_pcichild_device(struct hv_pcibus_device *hbus,
> get_pcichild(hpdev, hv_pcidev_ref_childlist);
> spin_lock_irqsave(&hbus->device_list_lock, flags);
>- /*
>- * When a device is being added to the bus, we set the PCI domain
>- * number to be the device serial number, which is non-zero and
>- * unique on the same VM. The serial numbers start with 1, and
>- * increase by 1 for each device. So device names including this
>- * can have shorter names than based on the bus instance UUID.
>- * Only the first device serial number is used for domain, so the
>- * domain number will not change after the first device is added.
>- */
>- if (list_empty(&hbus->children))
>- hbus->sysdata.domain = desc->ser;
> list_add_tail(&hpdev->list_entry, &hbus->children);
> spin_unlock_irqrestore(&hbus->device_list_lock, flags);
> return hpdev;
Hi Lorenzo,
Did you get a chance to look at the patch v5. Please let me know if
anything I need to address further.


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