From 97b6847ac10ba753849207e20df74a7c0ea03343 Mon Sep 17 00:00:00 2001 From: David Matlack Date: Wed, 16 Nov 2022 16:16:55 -0800 Subject: [PATCH] KVM: Cap vcpu->halt_poll_ns before halting rather than after Cap vcpu->halt_poll_ns based on the max halt polling time just before halting, rather than after the last halt. This arguably provides better accuracy if an admin disables halt polling in between halts, although the improvement is nominal. A side-effect of this change is that grow_halt_poll_ns() no longer needs to access vcpu->kvm->max_halt_poll_ns, which will be useful in a future commit where the max halt polling time can come from the module parameter halt_poll_ns instead. Signed-off-by: David Matlack Message-Id: <20221117001657.1067231-2-dmatlack@google.com> Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 25d7872b29c1..2a7285c14013 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3377,9 +3377,6 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu) if (val < grow_start) val = grow_start; - if (val > vcpu->kvm->max_halt_poll_ns) - val = vcpu->kvm->max_halt_poll_ns; - vcpu->halt_poll_ns = val; out: trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old); @@ -3492,11 +3489,16 @@ static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start, void kvm_vcpu_halt(struct kvm_vcpu *vcpu) { bool halt_poll_allowed = !kvm_arch_no_poll(vcpu); - bool do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns; ktime_t start, cur, poll_end; bool waited = false; + bool do_halt_poll; u64 halt_ns; + if (vcpu->halt_poll_ns > vcpu->kvm->max_halt_poll_ns) + vcpu->halt_poll_ns = vcpu->kvm->max_halt_poll_ns; + + do_halt_poll = halt_poll_allowed && vcpu->halt_poll_ns; + start = cur = poll_end = ktime_get(); if (do_halt_poll) { ktime_t stop = ktime_add_ns(start, vcpu->halt_poll_ns);