Re: [PATCH 04/12] pci-p2p: Clear ACS P2P flags for all client devices

[Logan Gunthorpe]

On 04/01/18 05:00 PM, Logan Gunthorpe wrote:
> 
> 
> On 04/01/18 03:35 PM, Alex Williamson wrote:
>> Yep, flipping these ACS bits invalidates any IOMMU groups that depend
>> on the isolation of that downstream port and I suspect also any peers
>> within the same PCI slot of that port and their downstream devices. The
>> entire sub-hierarchy grouping needs to be re-evaluated. This
>> potentially affects running devices that depend on that isolation, so
>> I'm not sure how that happens dynamically. A boot option might be
>> easier. Thanks,
> 

Also, considering this further: if you can point me to a way to tell if
a device is in an IOMMU group it should be pretty easy to disallow a
device that has been assigned to a group from being used in P2P
transactions.

Logan