From: Suravee Suthikulpanit suravee.suthikulpanit@amd.com
commit 4a204f7895878363ca8211f50ec610408c8c70aa upstream.
Expand KVM's mask for the AVIC host physical ID to the full 12 bits defined by the architecture. The number of bits consumed by hardware is model specific, e.g. early CPUs ignored bits 11:8, but there is no way for KVM to enumerate the "true" size. So, KVM must allow using all bits, else it risks rejecting completely legal x2APIC IDs on newer CPUs.
This means KVM relies on hardware to not assign x2APIC IDs that exceed the "true" width of the field, but presumably hardware is smart enough to tie the width to the max x2APIC ID. KVM also relies on hardware to support at least 8 bits, as the legacy xAPIC ID is writable by software. But, those assumptions are unavoidable due to the lack of any way to enumerate the "true" width.
Cc: stable@vger.kernel.org Cc: Maxim Levitsky mlevitsk@redhat.com Suggested-by: Sean Christopherson seanjc@google.com Reviewed-by: Sean Christopherson seanjc@google.com Fixes: 44a95dae1d22 ("KVM: x86: Detect and Initialize AVIC support") Signed-off-by: Suravee Suthikulpanit suravee.suthikulpanit@amd.com Message-Id: 20220211000851.185799-1-suravee.suthikulpanit@amd.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com [modified due to the conflict caused by the commit 391503528257 ("KVM: x86: SVM: move avic definitions from AMD's spec to svm.h")] Signed-off-by: Suravee Suthikulpanit suravee.suthikulpanit@amd.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/svm/avic.c | 7 +------ arch/x86/kvm/svm/svm.h | 2 +- 2 files changed, 2 insertions(+), 7 deletions(-)
--- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -949,15 +949,10 @@ out: void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { u64 entry; - /* ID = 0xff (broadcast), ID > 0xff (reserved) */ int h_physical_id = kvm_cpu_get_apicid(cpu); struct vcpu_svm *svm = to_svm(vcpu);
- /* - * Since the host physical APIC id is 8 bits, - * we can support host APIC ID upto 255. - */ - if (WARN_ON(h_physical_id > AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK)) + if (WARN_ON(h_physical_id & ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK)) return;
entry = READ_ONCE(*(svm->avic_physical_id_cache)); --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -510,7 +510,7 @@ extern struct kvm_x86_nested_ops svm_nes #define AVIC_LOGICAL_ID_ENTRY_VALID_BIT 31 #define AVIC_LOGICAL_ID_ENTRY_VALID_MASK (1 << 31)
-#define AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK (0xFFULL) +#define AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK GENMASK_ULL(11, 0) #define AVIC_PHYSICAL_ID_ENTRY_BACKING_PAGE_MASK (0xFFFFFFFFFFULL << 12) #define AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK (1ULL << 62) #define AVIC_PHYSICAL_ID_ENTRY_VALID_MASK (1ULL << 63)