[PATCH v4 11/12] KVM: mips, x86: do not rely on KVM_REQ_UNHALT

From: Sean Christopherson
Date: Tue Sep 20 2022 - 20:34:04 EST


From: Paolo Bonzini <pbonzini@xxxxxxxxxx>

KVM_REQ_UNHALT is a weird request that simply reports the value of
kvm_arch_vcpu_runnable() on exit from kvm_vcpu_halt(). Only
MIPS and x86 are looking at it, the others just clear it. Check
the state of the vCPU directly so that the request is handled
as a nop on all architectures.

No functional change intended, except for corner cases where an
event arrive immediately after a signal become pending or after
another similar host-side event.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/mips/kvm/emulate.c | 7 +++----
arch/x86/kvm/x86.c | 9 ++++++++-
2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index b494d8d39290..1d7c56defe93 100644
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -955,13 +955,12 @@ enum emulation_result kvm_mips_emul_wait(struct kvm_vcpu *vcpu)
kvm_vcpu_halt(vcpu);

/*
- * We we are runnable, then definitely go off to user space to
+ * We are runnable, then definitely go off to user space to
* check if any I/O interrupts are pending.
*/
- if (kvm_check_request(KVM_REQ_UNHALT, vcpu)) {
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
+ kvm_clear_request(KVM_REQ_UNHALT, vcpu);
+ if (kvm_arch_vcpu_runnable(vcpu))
vcpu->run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
- }
}

return EMULATE_DONE;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8aeacbc2bff9..8b1ff7e91ecb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10811,7 +10811,14 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu)
if (hv_timer)
kvm_lapic_switch_to_hv_timer(vcpu);

- if (!kvm_check_request(KVM_REQ_UNHALT, vcpu))
+ kvm_clear_request(KVM_REQ_UNHALT, vcpu);
+
+ /*
+ * If the vCPU is not runnable, a signal or another host event
+ * of some kind is pending; service it without changing the
+ * vCPU's activity state.
+ */
+ if (!kvm_arch_vcpu_runnable(vcpu))
return 1;
}

--
2.37.3.968.ga6b4b080e4-goog