| Message ID | 1641471612-34483-1-git-send-email-wanpengli@tencent.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] KVM: LAPIC: Enable timer posted-interrupt when mwait/hlt is advertised | expand |
On Thu, Jan 06, 2022, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@tencent.com> > > As commit 0c5f81dad46 (KVM: LAPIC: Inject timer interrupt via posted interrupt) > mentioned that the host admin should well tune the guest setup, so that vCPUs > are placed on isolated pCPUs, and with several pCPUs surplus for *busy* housekeeping. > It is better to disable mwait/hlt/pause vmexits to keep the vCPUs in non-root > mode. However, we may isolate pCPUs for other purpose like DPDK or we can make > some guests isolated and others not, we may lose vmx preemption timer/timer fastpath > due to not well tuned setup, and the checking in kvm_can_post_timer_interrupt() > is not enough. Let's guarantee mwait/hlt is advertised before enabling posted-interrupt > interrupt. vmx preemption timer/timer fastpath can continue to work if both of them > are not advertised. > > Reported-by: Aili Yao <yaoaili@kingsoft.com> > Cc: Aili Yao <yaoaili@kingsoft.com> > Cc: Sean Christopherson <seanjc@google.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- Reviewed-by: Sean Christopherson <seanjc@google.com>
kindly ping, :) On Thu, 6 Jan 2022 at 20:21, Wanpeng Li <kernellwp@gmail.com> wrote: > > From: Wanpeng Li <wanpengli@tencent.com> > > As commit 0c5f81dad46 (KVM: LAPIC: Inject timer interrupt via posted interrupt) > mentioned that the host admin should well tune the guest setup, so that vCPUs > are placed on isolated pCPUs, and with several pCPUs surplus for *busy* housekeeping. > It is better to disable mwait/hlt/pause vmexits to keep the vCPUs in non-root > mode. However, we may isolate pCPUs for other purpose like DPDK or we can make > some guests isolated and others not, we may lose vmx preemption timer/timer fastpath > due to not well tuned setup, and the checking in kvm_can_post_timer_interrupt() > is not enough. Let's guarantee mwait/hlt is advertised before enabling posted-interrupt > interrupt. vmx preemption timer/timer fastpath can continue to work if both of them > are not advertised. > > Reported-by: Aili Yao <yaoaili@kingsoft.com> > Cc: Aili Yao <yaoaili@kingsoft.com> > Cc: Sean Christopherson <seanjc@google.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > v1 -> v2: > * also check kvm_hlt_in_guest since sometime mwait is disabled on host > > arch/x86/kvm/lapic.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index f206fc3..fdb7c81 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -113,7 +113,8 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic) > > static bool kvm_can_post_timer_interrupt(struct kvm_vcpu *vcpu) > { > - return pi_inject_timer && kvm_vcpu_apicv_active(vcpu); > + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) && > + (kvm_mwait_in_guest(vcpu->kvm) || kvm_hlt_in_guest(vcpu->kvm)); > } > > bool kvm_can_use_hv_timer(struct kvm_vcpu *vcpu) > -- > 2.7.4 >
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index f206fc3..fdb7c81 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -113,7 +113,8 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic) static bool kvm_can_post_timer_interrupt(struct kvm_vcpu *vcpu) { - return pi_inject_timer && kvm_vcpu_apicv_active(vcpu); + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) && + (kvm_mwait_in_guest(vcpu->kvm) || kvm_hlt_in_guest(vcpu->kvm)); } bool kvm_can_use_hv_timer(struct kvm_vcpu *vcpu)