Messages in this thread | | | Date | Wed, 27 Apr 2022 18:16:21 +0200 | Subject | Re: [PATCH MANUALSEL 5.17 3/7] x86/kvm: Preserve BSP MSR_KVM_POLL_CONTROL across suspend/resume | From | Paolo Bonzini <> |
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On 4/27/22 17:53, Sasha Levin wrote: > From: Wanpeng Li <wanpengli@tencent.com> > > [ Upstream commit 0361bdfddca20c8855ea3bdbbbc9c999912b10ff ] > > MSR_KVM_POLL_CONTROL is cleared on reset, thus reverting guests to > host-side polling after suspend/resume. Non-bootstrap CPUs are > restored correctly by the haltpoll driver because they are hot-unplugged > during suspend and hot-plugged during resume; however, the BSP > is not hotpluggable and remains in host-sde polling mode after > the guest resume. The makes the guest pay for the cost of vmexits > every time the guest enters idle. > > Fix it by recording BSP's haltpoll state and resuming it during guest > resume. > > Cc: Marcelo Tosatti <mtosatti@redhat.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > Message-Id: <1650267752-46796-1-git-send-email-wanpengli@tencent.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > Signed-off-by: Sasha Levin <sashal@kernel.org> > --- > arch/x86/kernel/kvm.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index ed8a13ac4ab2..4c2a158bb6c4 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -69,6 +69,7 @@ static DEFINE_PER_CPU_DECRYPTED(struct kvm_vcpu_pv_apf_data, apf_reason) __align > DEFINE_PER_CPU_DECRYPTED(struct kvm_steal_time, steal_time) __aligned(64) __visible; > static int has_steal_clock = 0; > > +static int has_guest_poll = 0; > /* > * No need for any "IO delay" on KVM > */ > @@ -706,14 +707,26 @@ static int kvm_cpu_down_prepare(unsigned int cpu) > > static int kvm_suspend(void) > { > + u64 val = 0; > + > kvm_guest_cpu_offline(false); > > +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL > + if (kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) > + rdmsrl(MSR_KVM_POLL_CONTROL, val); > + has_guest_poll = !(val & 1); > +#endif > return 0; > } > > static void kvm_resume(void) > { > kvm_cpu_online(raw_smp_processor_id()); > + > +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL > + if (kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL) && has_guest_poll) > + wrmsrl(MSR_KVM_POLL_CONTROL, 0); > +#endif > } > > static struct syscore_ops kvm_syscore_ops = {
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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