Do nothing in kvm_lapic_set_base() if the APIC base MSR value is the same as the current value. All flows except the handling of the base address explicitly take effect if and only if relevant bits are changing. For the base address, invoking kvm_lapic_set_base() before KVM initializes the base to APIC_DEFAULT_PHYS_BASE during vCPU RESET would be a KVM bug, i.e. KVM _must_ initialize apic->base_address before exposing the vCPU (to userspace or KVM at-large). Note, the inhibit is intended to be set if the base address is _changed_ from the default, i.e. is also covered by the RESET behavior. Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx> Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Link: https://lore.kernel.org/r/20241009181742.1128779-2-seanjc@xxxxxxxxxx Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/lapic.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 65412640cfc7..8fe63f719254 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -2582,6 +2582,9 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value) u64 old_value = vcpu->arch.apic_base; struct kvm_lapic *apic = vcpu->arch.apic; + if (old_value == value) + return; + vcpu->arch.apic_base = value; if ((old_value ^ value) & MSR_IA32_APICBASE_ENABLE) -- 2.47.0.163.g1226f6d8fa-goog
