I would make the subject: Revert "PCI: hv: Use device serial number as PCI domain"
so it matches the original commit. Otherwise you really need quite a lot of driver internal knowledge to connect them. On Wed, Apr 11, 2018 at 12:36:25AM +0000, Sridhar Pitchai wrote: > 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. Possible alternate text: The reason for that patch was to have a consistent and short name for the device, but Hyper-V doesn't provide unique serial numbers (in spite of the code comment claiming that it does). Using non-unique serial numbers as domain IDs leads to duplicate device addresses, which causes PCI bus registration to fail. > 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. I think the above sentence is redundant and could be removed. > Revert commit 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI > domain") so we can reliably support multiple devices being assigned to > a guest. > > Fixes: 4a9b0933bdfc ("PCI: hv: Use device serial number as PCI domain") > Signed-off-by: Sridhar Pitchai <sridhar.pitc...@microsoft.com> > Cc: sta...@vger.kernel.org Regardless of what you do with the feedback above, Reviewed-by: Bjorn Helgaas <bhelg...@google.com> Thanks a lot for persisting with this! > --- > Changes in v6: > * fix the commit comment. [Lorenzo Pieralisi, Bjorn Helgaas] > --- > 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; > -- > 2.14.1 > _______________________________________________ devel mailing list de...@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel