On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote: > Invoke the arch hooks for block+unblock if and only if KVM actually > attempts to block the vCPU. The only non-nop implementation is on x86, > specifically SVM's AVIC, and there is no need to put the AVIC prior to > halt-polling as KVM x86's kvm_vcpu_has_events() will scour the full vIRR > to find pending IRQs regardless of whether the AVIC is loaded/"running". > > The primary motivation is to allow future cleanup to split out "block" > from "halt", but this is also likely a small performance boost on x86 SVM > when halt-polling is successful. > > Adjust the post-block path to update "cur" after unblocking, i.e. include > AVIC load time in halt_wait_ns and halt_wait_hist, so that the behavior > is consistent. Moving just the pre-block arch hook would result in only > the AVIC put latency being included in the halt_wait stats. There is no > obvious evidence that one way or the other is correct, so just ensure KVM > is consistent. > > Note, x86 has two separate paths for handling APICv with respect to vCPU > blocking. VMX uses hooks in x86's vcpu_block(), while SVM uses the arch > hooks in kvm_vcpu_block(). Prior to this path, the two paths were more > or less functionally identical. That is very much not the case after > this patch, as the hooks used by VMX _must_ fire before halt-polling. > x86's entire mess will be cleaned up in future patches. > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > --- > virt/kvm/kvm_main.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index f90b3ed05628..227f6bbe0716 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -3235,8 +3235,6 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > bool waited = false; > u64 block_ns; > > - kvm_arch_vcpu_blocking(vcpu); > - > start = cur = poll_end = ktime_get(); > if (do_halt_poll) { > ktime_t stop = ktime_add_ns(ktime_get(), vcpu->halt_poll_ns); > @@ -3253,6 +3251,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > } while (kvm_vcpu_can_poll(cur, stop)); > } > > + kvm_arch_vcpu_blocking(vcpu); > > prepare_to_rcuwait(wait); > for (;;) { > @@ -3265,6 +3264,9 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > schedule(); > } > finish_rcuwait(wait); > + > + kvm_arch_vcpu_unblocking(vcpu); > + > cur = ktime_get(); > if (waited) { > vcpu->stat.generic.halt_wait_ns += > @@ -3273,7 +3275,6 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > ktime_to_ns(cur) - ktime_to_ns(poll_end)); > } > out: > - kvm_arch_vcpu_unblocking(vcpu); > block_ns = ktime_to_ns(cur) - ktime_to_ns(start); > > /* Makes sense. Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx> Best regards, Maxim Levitsky _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm