Commit 14aecf2a authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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



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: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarBinbin Wu <binbin.wu@linux.intel.com>
Message-ID: <20250222014757.897978-6-binbin.wu@linux.intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 24c12911

arch/x86/kvm/lapic.c

+10 −1
Original line number Diff line number Diff line
@@ -1797,8 +1797,17 @@ static void apic_update_lvtt(struct kvm_lapic *apic) 
static bool lapic_timer_int_injected(struct kvm_vcpu *vcpu)

{

	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)) {

		int vec = reg & APIC_VECTOR_MASK;

		void *bitmap = apic->regs + APIC_ISR;