[Intel-wired-lan] PCI ACS quirk for X710/XL710?

Alex Williamson alex.williamson at redhat.com
Tue Dec 1 17:57:17 UTC 2015

On Tue, 2015-12-01 at 10:19 -0600, Chris Friesen wrote:
> On 12/01/2015 10:07 AM, Chris Friesen wrote:
> > Hi all,
> >
> > The three of you in the "to" list were involved with adding commits d748804 and
> > 100ebb2 to address the fact that these multi-port NICs will not do peer-to-peer
> > between functions, but do not report this via ACS.
> >
> > We've got an X710 device (PCI device 0x1572, driver version 1.3.1-k, firmware
> > 4.40) and we're seeing all the ports being assigned to the same IOMMU group.
> >
> > I'm guessing that this is due to a lack of ACS, and that it would be valid to
> > add the X710/XL710 PCI IDs to the pci_dev_acs_enabled table.  Could someone from
> > Intel confirm this?
> Looking at the datasheet (I suppose I should have done that first, sorry) it 
> looks like this device supports ACS.  However, we're still seeing all the ports 
> being placed into the same IOMMU group.
> Is there a way to prevent/disable this behaviour?  We want to be able to assign 
> each port to a separate VM, and thus for our purposes they need to be in 
> separate IOMMU groups.

Are you sure the grouping isn't caused by the root port and not the X710
endpoints?  Please provide:

$ find /sys/kernel/iommu_groups/ -type l

$ sudo lspci -vvv

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