On 14/05/19 17:49, Suthikulpanit, Suravee wrote: > Current logic does not allow VCPU to be loaded onto CPU with > APIC ID 255. This should be allowed since the host physical APIC ID > field in the AVIC Physical APIC table entry is an 8-bit value, > and APIC ID 255 is valid in system with x2APIC enabled. > Instead, do not allow VCPU load if the host APIC ID cannot be > represented by an 8-bit value. > > Also, use the more appropriate AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK > instead of AVIC_MAX_PHYSICAL_ID_COUNT. > > Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx> Queued, with Cc to stable and using "kvm: svm/avic: fix off-by-one in checking host APIC ID" as the subject. Paolo > --- > > Change in V2: > * Use AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK instead of > AVIC_MAX_PHYSICAL_ID_COUNT. > > arch/x86/kvm/svm.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 687767f..345fe9e 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -2071,7 +2071,11 @@ static void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > if (!kvm_vcpu_apicv_active(vcpu)) > return; > > - if (WARN_ON(h_physical_id >= AVIC_MAX_PHYSICAL_ID_COUNT)) > + /* > + * 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)) > return; > > entry = READ_ONCE(*(svm->avic_physical_id_cache)); >
