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