linux-kernel - [PATCH v2 09/10] KVM: selftests: Verify the guest can read back the x2APIC ICR it wrote

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Message-ID: <20240719235107.3023592-10-seanjc@google.com>
Date: Fri, 19 Jul 2024 16:51:06 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Maxim Levitsky <mlevitsk@...hat.com>, Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v2 09/10] KVM: selftests: Verify the guest can read back the
 x2APIC ICR it wrote

Now that the BUSY bit mess is gone (for x2APIC), verify that the *guest*
can read back the ICR value that it wrote.  Due to the divergent
behavior between AMD and Intel with respect to the backing storage of the
ICR in the vAPIC page, emulating a seemingly simple MSR write is quite
complex.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 tools/testing/selftests/kvm/x86_64/xapic_state_test.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 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 d701fe9dd686..a940adf429ef 100644
--- a/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
@@ -45,10 +45,12 @@ static void x2apic_guest_code(void)
 		uint64_t val = x2apic_read_reg(APIC_IRR) |
 			       x2apic_read_reg(APIC_IRR + 0x10) << 32;
 
-		if (val & X2APIC_RSVD_BITS_MASK)
+		if (val & X2APIC_RSVD_BITS_MASK) {
 			x2apic_write_reg_fault(APIC_ICR, val);
-		else
+		} else {
 			x2apic_write_reg(APIC_ICR, val);
+			GUEST_ASSERT_EQ(x2apic_read_reg(APIC_ICR), val);
+		}
 		GUEST_SYNC(val);
 	} while (1);
 }
-- 
2.45.2.1089.g2a221341d9-goog