On 30.08.24 11:35, Vitaly Kuznetsov wrote: > Sean Christopherson <seanjc@xxxxxxxxxx> writes: > >> Unconditionally honor guest PAT on CPUs that support self-snoop, as >> Intel has confirmed that CPUs that support self-snoop always snoop caches >> and store buffers. I.e. CPUs with self-snoop maintain cache coherency >> even in the presence of aliased memtypes, thus there is no need to trust >> the guest behaves and only honor PAT as a last resort, as KVM does today. >> >> Honoring guest PAT is desirable for use cases where the guest has access >> to non-coherent DMA _without_ bouncing through VFIO, e.g. when a virtual >> (mediated, for all intents and purposes) GPU is exposed to the guest, along >> with buffers that are consumed directly by the physical GPU, i.e. which >> can't be proxied by the host to ensure writes from the guest are performed >> with the correct memory type for the GPU. > > Necroposting! > > Turns out that this change broke "bochs-display" driver in QEMU even > when the guest is modern (don't ask me 'who the hell uses bochs for > modern guests', it was basically a configuration error :-). E.g: > [...] This regression made it to the list of tracked regressions. It seems this thread stalled a while ago. Was this ever fixed? Does not look like it, but I might have missed something. Or is this a regression I should just ignore for one reason or another? Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) -- Everything you wanna know about Linux kernel regression tracking: https://linux-regtracking.leemhuis.info/about/#tldr If I did something stupid, please tell me, as explained on that page. #regzbot poke
