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KVM: x86: Assume timer IRQ was injected if APIC state is protected

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If APIC state is protected, i.e. the vCPU is a TDX guest, assume a timer
IRQ was injected when deciding whether or not to busy wait in the "timer
advanced" path.  The "real" vIRR is not readable/writable, so trying to
query for a pending timer IRQ will return garbage.

Note, TDX can scour the PIR if it wants to be more precise and skip the
"wait" call entirely.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Message-ID: <20250222014757.897978-6-binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2025-02-22 09:47:46 +08:00 committed by Paolo Bonzini
parent 24c1291116
commit 14aecf2a5b
1 changed files with 10 additions and 1 deletions
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11
arch/x86/kvm/lapic.c
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@ -1797,8 +1797,17 @@ static void apic_update_lvtt(struct kvm_lapic *apic)
static bool lapic_timer_int_injected(struct kvm_vcpu *vcpu) static bool lapic_timer_int_injected(struct kvm_vcpu *vcpu)
{ {
struct kvm_lapic *apic = vcpu->arch.apic; struct kvm_lapic *apic = vcpu->arch.apic;
u32 reg = kvm_lapic_get_reg(apic, APIC_LVTT); u32 reg;
/*
* Assume a timer IRQ was "injected" if the APIC is protected. KVM's
* copy of the vIRR is bogus, it's the responsibility of the caller to
* precisely check whether or not a timer IRQ is pending.
*/
if (apic->guest_apic_protected)
return true;
reg = kvm_lapic_get_reg(apic, APIC_LVTT);
if (kvm_apic_hw_enabled(apic)) { if (kvm_apic_hw_enabled(apic)) {
int vec = reg & APIC_VECTOR_MASK; int vec = reg & APIC_VECTOR_MASK;
void *bitmap = apic->regs + APIC_ISR; void *bitmap = apic->regs + APIC_ISR;