From: Sean Christopherson Date: Fri, 12 Jun 2026 18:54:59 +0000 (-0700) Subject: x86/apic: KVM: Use cpu_physical_id() to get APIC ID of running vCPU for AVIC X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=098e32cba334da0f3fa8cfd4e022ae7c72341400;p=thirdparty%2Fkernel%2Fstable.git x86/apic: KVM: Use cpu_physical_id() to get APIC ID of running vCPU for AVIC Use cpu_physical_id() instead of default_cpu_present_to_apicid() when getting the APIC ID of the pCPU on which a vCPU is running/loaded, as the kernel has gone way off the rails if a vCPU is loaded on a pCPU that has been physically removed from the system. Even if the impossible were to happen, the absolutely worst case scenario is that hardware will ring the AIVC doorbell on the wrong pCPU, i.e. a severely broken system will experience mild performance issues. Kill off KVM's superfluous kvm_cpu_get_apicid() wrapper along with the for-KVM export of default_cpu_present_to_apicid(), as they existed purely for the wonky AVIC usage. Cc: Kai Huang Cc: Yosry Ahmed Signed-off-by: Sean Christopherson Acked-by: Naveen N Rao (AMD) Reviewed-by: Kai Huang Reviewed-by: Yosry Ahmed Message-ID: <20260612185459.591892-1-seanjc@google.com> Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 9347c2b62cba4..5f6c1ce9673b7 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -2525,16 +2525,6 @@ static inline void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu) kvm_x86_call(vcpu_unblocking)(vcpu); } -static inline int kvm_cpu_get_apicid(int mps_cpu) -{ -#ifdef CONFIG_X86_LOCAL_APIC - return default_cpu_present_to_apicid(mps_cpu); -#else - WARN_ON_ONCE(1); - return BAD_APICID; -#endif -} - int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages); #define KVM_CLOCK_VALID_FLAGS \ diff --git a/arch/x86/kernel/apic/apic_common.c b/arch/x86/kernel/apic/apic_common.c index 2ed3b5c88c7f0..45e6b816353ed 100644 --- a/arch/x86/kernel/apic/apic_common.c +++ b/arch/x86/kernel/apic/apic_common.c @@ -26,7 +26,6 @@ u32 default_cpu_present_to_apicid(int mps_cpu) else return BAD_APICID; } -EXPORT_SYMBOL_FOR_KVM(default_cpu_present_to_apicid); /* * Set up the logical destination ID when the APIC operates in logical diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index 0726f88e679aa..58e493a80cb0e 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -460,8 +460,8 @@ void avic_ring_doorbell(struct kvm_vcpu *vcpu) int cpu = READ_ONCE(vcpu->cpu); if (cpu != get_cpu()) { - wrmsrq(MSR_AMD64_SVM_AVIC_DOORBELL, kvm_cpu_get_apicid(cpu)); - trace_kvm_avic_doorbell(vcpu->vcpu_id, kvm_cpu_get_apicid(cpu)); + wrmsrq(MSR_AMD64_SVM_AVIC_DOORBELL, cpu_physical_id(cpu)); + trace_kvm_avic_doorbell(vcpu->vcpu_id, cpu_physical_id(cpu)); } put_cpu(); } @@ -1013,7 +1013,7 @@ static void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu, enum avic_vcpu_action action) { struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm); - int h_physical_id = kvm_cpu_get_apicid(cpu); + int h_physical_id = cpu_physical_id(cpu); struct vcpu_svm *svm = to_svm(vcpu); unsigned long flags; u64 entry;