From 74d76947b1dc6389941e90e4a8452b89b8b239ce Mon Sep 17 00:00:00 2001 From: "Suthikulpanit, Suravee" Date: Tue, 14 May 2019 15:49:52 +0000 Subject: [PATCH] kvm: svm/avic: fix off-by-one in checking host APIC ID commit c9bcd3e3335d0a29d89fabd2c385e1b989e6f1b0 upstream. 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 Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- 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 1296e44fd969..3a7e79f6cc77 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1567,7 +1567,11 @@ 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));