Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > On 25/05/20 16:41, Vitaly Kuznetsov wrote: >> Concerns were expressed around APF events delivery when CPU is not >> in user mode (KVM_ASYNC_PF_SEND_ALWAYS), e.g. >> https://lore.kernel.org/kvm/ed71d0967113a35f670a9625a058b8e6e0b2f104.1583547991.git.luto@xxxxxxxxxx/ >> >> 'Page ready' events are already free from '#PF abuse' but 'page not ready' >> notifications still go through #PF (to be changed in the future). Make the >> probability of running into issues when APF collides with regular #PF lower >> by deprecating KVM_ASYNC_PF_SEND_ALWAYS. The feature doesn't seem to be >> important enough for any particular workload to notice the difference. > > This has been disabled already in guest code, but I don't see a > particular reason to deprecate it in the host too. Supporting it on the > host is just one line of code; if it's a problem *for the guest*, you > just don't use KVM_ASYNC_PF_SEND_ALWAYS. > > Also, note that #VE will always be delivered to the guest even at CPL0; > the decision on whether to do sync or async page fault at CPL0 will move > to the guest, but enabling #VE will probably _require_ the > KVM_ASYNC_PF_SEND_ALWAYS bit to be set (and KVM_ASYNC_PF_DELIVERY_AS_INT > as well). I actually missed the fact that guest side is already disabled (I can see it now in the queue), feel free to ignore this patch then. -- Vitaly
