When AVIC, and thus IPI virtualization on AMD, is enabled, the CPU will
virtualize ICR writes. Unfortunately, the CPU doesn't do a very good job,
as it fails to clear the BUSY bit and also allows writing ICR2[23:0],
despite them being "RESERVED MBZ". Account for the quirky behavior in
the xapic_state test to avoid failures in a configuration that likely has
no hope of ever being enabled in production.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
.../selftests/kvm/x86_64/xapic_state_test.c | 23 +++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/kvm/x86_64/xapic_state_test.c b/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
index a940adf429ef..a72bdc4c5c52 100644
--- a/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
@@ -13,6 +13,7 @@
struct xapic_vcpu {
struct kvm_vcpu *vcpu;
bool is_x2apic;
+ bool has_xavic_errata;
};
static void xapic_guest_code(void)
@@ -79,12 +80,17 @@ static void ____test_icr(struct xapic_vcpu *x, uint64_t val)
vcpu_ioctl(vcpu, KVM_GET_LAPIC, &xapic);
icr = (u64)(*((u32 *)&xapic.regs[APIC_ICR])) |
(u64)(*((u32 *)&xapic.regs[APIC_ICR2])) << 32;
- if (!x->is_x2apic)
- val &= (-1u | (0xffull << (32 + 24)));
- else if (val & X2APIC_RSVD_BITS_MASK)
+ if (!x->is_x2apic) {
+ if (!x->has_xavic_errata)
+ val &= (-1u | (0xffull << (32 + 24)));
+ } else if (val & X2APIC_RSVD_BITS_MASK) {
return;
+ }
- TEST_ASSERT_EQ(icr, val & ~APIC_ICR_BUSY);
+ if (x->has_xavic_errata)
+ TEST_ASSERT_EQ(icr & ~APIC_ICR_BUSY, val & ~APIC_ICR_BUSY);
+ else
+ TEST_ASSERT_EQ(icr, val & ~APIC_ICR_BUSY);
}
static void __test_icr(struct xapic_vcpu *x, uint64_t val)
@@ -209,6 +215,15 @@ int main(int argc, char *argv[])
vm = vm_create_with_one_vcpu(&x.vcpu, xapic_guest_code);
x.is_x2apic = false;
+ /*
+ * AMD's AVIC implementation is buggy (fails to clear the ICR BUSY bit),
+ * and also diverges from KVM with respect to ICR2[23:0] (KVM and Intel
+ * drops writes, AMD does not). Account for the errata when checking
+ * that KVM reads back what was written.
+ */
+ x.has_xavic_errata = host_cpu_is_amd &&
+ get_kvm_amd_param_bool("avic");
+
vcpu_clear_cpuid_feature(x.vcpu, X86_FEATURE_X2APIC);
virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
--
2.45.2.1089.g2a221341d9-goog
