[PATCH] KVM: selftests: Enhance handling WRMSR ICR register in x2APIC mode

[Paolo Bonzini]

From: Zeng Guang <guang.zeng@xxxxxxxxx>

Hardware would directly write x2APIC ICR register instead of software
emulation in some circumstances, e.g when Intel IPI virtualization is
enabled. This behavior requires normal reserved bits checking to ensure
them input as zero, otherwise it will cause #GP. So we need mask out
those reserved bits from the data written to vICR register.

Remove Delivery Status bit emulation in test case as this flag
is invalid and not needed in x2APIC mode. KVM may ignore clearing
it during interrupt dispatch which will lead to fake test failure.

Opportunistically correct vector number for test sending IPI to
non-existent vCPUs.

Signed-off-by: Zeng Guang <guang.zeng@xxxxxxxxx>
Message-Id: <20220623094511.26066-1-guang.zeng@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 .../selftests/kvm/x86_64/xapic_state_test.c   | 20 ++++++++++++++++---
 1 file changed, 17 insertions(+), 3 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 5c5dc7bbb4e2..87531623064f 100644
--- a/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
@@ -71,13 +71,27 @@ 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)
+	if (!x->is_x2apic) {
 		val &= (-1u | (0xffull << (32 + 24)));
-	ASSERT_EQ(icr, val & ~APIC_ICR_BUSY);
+		ASSERT_EQ(icr, val & ~APIC_ICR_BUSY);
+	} else {
+		ASSERT_EQ(icr & ~APIC_ICR_BUSY, val & ~APIC_ICR_BUSY);
+	}
 }
 
+#define X2APIC_RSVED_BITS_MASK  (GENMASK_ULL(31,20) | \
+				 GENMASK_ULL(17,16) | \
+				 GENMASK_ULL(13,13))
+
 static void __test_icr(struct xapic_vcpu *x, uint64_t val)
 {
+	if (x->is_x2apic) {
+		/* Hardware writing vICR register requires reserved bits 31:20,
+		 * 17:16 and 13 kept as zero to avoid #GP exception. Data value
+		 * written to vICR should mask out those bits above.
+		 */
+		val &= ~X2APIC_RSVED_BITS_MASK;
+	}
 	____test_icr(x, val | APIC_ICR_BUSY);
 	____test_icr(x, val & ~(u64)APIC_ICR_BUSY);
 }
@@ -102,7 +116,7 @@ static void test_icr(struct xapic_vcpu *x)
 	icr = APIC_INT_ASSERT | 0xff;
 	for (i = vcpu->id + 1; i < 0xff; i++) {
 		for (j = 0; j < 8; j++)
-			__test_icr(x, i << (32 + 24) | APIC_INT_ASSERT | (j << 8));
+			__test_icr(x, i << (32 + 24) | icr | (j << 8));
 	}
 
 	/* And again with a shorthand destination for all types of IPIs. */
-- 
2.31.1