Messages in this thread |  | | Date | Wed, 27 Oct 2021 17:36:18 +0200 | Subject | Re: [PATCH v2 35/43] KVM: SVM: Signal AVIC doorbell iff vCPU is in guest mode | From | Paolo Bonzini <> |
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On 27/10/21 17:06, Sean Christopherson wrote: >> Does this still need to check the "running" flag? That should be a strict >> superset of vcpu->mode == IN_GUEST_MODE. > > No. Signalling the doorbell when "running" is set but the vCPU is not in the > guest is just an expensive nop. So even if KVM were to rework its handling of > "running" to set the flag immediately before VMRUN and clear it immediately after, > keying off IN_GUEST_MODE and not "running" would not be wrong, just sub-optimal. > > I doubt KVM will ever make the "running" flag super precise, because keeping the > flag set when the vCPU is loaded avoids VM-Exits on other vCPUs due to undelivered > IPIs.
Right, so should we drop the "if (running)" check in this patch, at the same time as it's adding the IN_GUEST_MODE check?
Paolo
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