On Tue, Jun 10, 2025 at 01:30:45PM -0300, Jason Gunthorpe wrote: > On Tue, Jun 10, 2025 at 04:37:58PM +0100, Robin Murphy wrote: > > On 2025-06-09 7:45 pm, Nicolin Chen wrote: > > > Hi all, > > > > > > Per PCIe r6.3, sec 10.3.1 IMPLEMENTATION NOTE, software should disable ATS > > > before initiating a Function Level Reset, and then ensure no invalidation > > > requests being issued to a device when its ATS capability is disabled. > > > > Not really - what it says is that software should not expect to receive > > invalidate completions from a function which is in the process of being > > reset or powered off, and if software doesn't want to be confused by that > > then it should take care to wait for completion or timeout of all > > outstanding requests, and avoid issuing new requests, before initiating such > > a reset or power transition. > > The commit message can be more precise, but I agree with the > conclusion that the right direction for Linux is to disable and block > ATS, instead of trying to ignore completion time out events, or trying > to block page table mutations. Ie do what the implementation note > says.. > > Maybe: > > PCIe permits a device to ignore ATS invalidation TLPs while it is > processing FLR. This creates a problem visible to the OS where ATS > invalidation commands will time out. For instance a SVA domain will > have no coordination with a FLR event and can racily issue ATC > invalidations into a resetting device. The sec 10.3.1 implementation note mentions FLR specifically, but it seems like *any* kind of reset would be vulnerable, e.g., SBR, external PERST# assert, etc?
