KVM: x86: Invoke kvm_vcpu_block() directly for non-HALTED wait states

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.

Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-19-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9d628ec384144c1ef1808141ff2b0a2662327b13..50450ebe709fa41d7c3319489255ed1bd1332406 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10006,7 +10006,10 @@ 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)