| Message ID | 20210925005528.1145584-15-seanjc@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: Halt-polling fixes, cleanups and a new stat | expand |
On Fri, Sep 24, 2021 at 05:55:28PM -0700, Sean Christopherson wrote: > Call kvm_vcpu_block() directly for all wait states except HALTED so that > kvm_vcpu_halt() is no longer a misnomer on x86. > > Functionally, this means KVM will never attempt halt-polling or adjust > vcpu->halt_poll_ns for INIT_RECEIVED (a.k.a. Wait-For-SIPI (WFS)) or > AP_RESET_HOLD; UNINITIALIZED is handled in kvm_arch_vcpu_ioctl_run(), > and x86 doesn't use any other "wait" states. > > As mentioned above, the motivation of this is purely so that "halt" isn't > overloaded on x86, e.g. in KVM's stats. Skipping halt-polling for WFS > (and RESET_HOLD) has no meaningful effect on guest performance as there > are typically single-digit numbers of INIT-SIPI sequences per AP vCPU, > per boot, versus thousands of HLTs just to boot to console. > > Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: David Matlack <dmatlack@google.com> > --- > arch/x86/kvm/x86.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index b444f9315766..a0f313c4bc49 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9893,7 +9893,10 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu) > if (!kvm_arch_vcpu_runnable(vcpu) && > (!kvm_x86_ops.pre_block || static_call(kvm_x86_pre_block)(vcpu) == 0)) { > srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx); > - kvm_vcpu_halt(vcpu); > + if (vcpu->arch.mp_state == KVM_MP_STATE_HALTED) > + kvm_vcpu_halt(vcpu); > + else > + kvm_vcpu_block(vcpu); > vcpu->srcu_idx = srcu_read_lock(&kvm->srcu); > > if (kvm_x86_ops.post_block) > -- > 2.33.0.685.g46640cef36-goog >
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b444f9315766..a0f313c4bc49 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9893,7 +9893,10 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu) if (!kvm_arch_vcpu_runnable(vcpu) && (!kvm_x86_ops.pre_block || static_call(kvm_x86_pre_block)(vcpu) == 0)) { srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx); - kvm_vcpu_halt(vcpu); + if (vcpu->arch.mp_state == KVM_MP_STATE_HALTED) + kvm_vcpu_halt(vcpu); + else + kvm_vcpu_block(vcpu); vcpu->srcu_idx = srcu_read_lock(&kvm->srcu); if (kvm_x86_ops.post_block)
Call kvm_vcpu_block() directly for all wait states except HALTED so that kvm_vcpu_halt() is no longer a misnomer on x86. Functionally, this means KVM will never attempt halt-polling or adjust vcpu->halt_poll_ns for INIT_RECEIVED (a.k.a. Wait-For-SIPI (WFS)) or AP_RESET_HOLD; UNINITIALIZED is handled in kvm_arch_vcpu_ioctl_run(), and x86 doesn't use any other "wait" states. As mentioned above, the motivation of this is purely so that "halt" isn't overloaded on x86, e.g. in KVM's stats. Skipping halt-polling for WFS (and RESET_HOLD) has no meaningful effect on guest performance as there are typically single-digit numbers of INIT-SIPI sequences per AP vCPU, per boot, versus thousands of HLTs just to boot to console. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/x86.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)