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SubjectRe: [PATCH v2 10/10] KVM: x86: deprecate KVM_ASYNC_PF_SEND_ALWAYS
Paolo Bonzini <> 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.
>> '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
> 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.


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