Messages in this thread | | | Date | Mon, 25 Oct 2021 17:21:55 +0200 | Subject | Re: [PATCH v2 0/4] KVM: x86: APICv cleanups | From | Paolo Bonzini <> |
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On 25/10/21 16:35, Sean Christopherson wrote: >> So yeah, I think you're right. > Yep. The alternative would be to explicitly check for a pending APICv update. > I don't have a strong opinion, I dislike both options equally:-)
No, checking for the update is worse and with this example, I can now point my finger on why I preferred the VM check even before: because even though the page fault path runs in vCPU context and uses a vCPU-specific role, overall the page tables are still per-VM.
Therefore it makes sense for the page fault path to synchronize with whoever updates the flag and zaps the page, and not with the KVM_REQ_* handler of the same vCPU.
(Here goes the usual shameless plug of my lockless programming articles on LWN---I think you're old enough to vaguely remember Jerry Pournelle---and in particular the first one at https://lwn.net/Articles/844224/).
> Want me to type up a v3 comment?
Yes, please do.
Paolo
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