Re: [PATCH v3 3/9] KVM: x86: Defer tick-based accounting 'til after IRQ handling

[Frederic Weisbecker]

On Thu, Apr 15, 2021 at 03:21:00PM -0700, Sean Christopherson wrote:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> 
> When using tick-based accounting, defer the call to account guest time
> until after servicing any IRQ(s) that happened in the guest or
> immediately after VM-Exit.  Tick-based accounting of vCPU time relies on
> PF_VCPU being set when the tick IRQ handler runs, and IRQs are blocked
> throughout {svm,vmx}_vcpu_enter_exit().

Out of curiosity, how has guest accounting ever managed to work if we have always
cleared PF_VCPU before re-enabling interrupt?

Thanks.