linux-kernel - [PATCH 6/8] KVM: selftests: Add x86 helpers to play nice with x2APIC MSR #GPs

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Message-ID: <20240719234346.3020464-7-seanjc@google.com>
Date: Fri, 19 Jul 2024 16:43:43 -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 6/8] KVM: selftests: Add x86 helpers to play nice with x2APIC
 MSR #GPs

Add helpers to allow and expect #GP on x2APIC MSRs, and opportunistically
have the existing helper spit out a more useful error message if an
unexpected exception occurs.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 .../selftests/kvm/include/x86_64/apic.h       | 21 ++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/apic.h b/tools/testing/selftests/kvm/include/x86_64/apic.h
index 0f268b55fa06..51990094effd 100644
--- a/tools/testing/selftests/kvm/include/x86_64/apic.h
+++ b/tools/testing/selftests/kvm/include/x86_64/apic.h
@@ -11,6 +11,7 @@
 #include <stdint.h>
 
 #include "processor.h"
+#include "ucall_common.h"
 
 #define APIC_DEFAULT_GPA		0xfee00000ULL
 
@@ -93,9 +94,27 @@ static inline uint64_t x2apic_read_reg(unsigned int reg)
 	return rdmsr(APIC_BASE_MSR + (reg >> 4));
 }
 
+static inline uint8_t x2apic_write_reg_safe(unsigned int reg, uint64_t value)
+{
+	return wrmsr_safe(APIC_BASE_MSR + (reg >> 4), value);
+}
+
 static inline void x2apic_write_reg(unsigned int reg, uint64_t value)
 {
-	wrmsr(APIC_BASE_MSR + (reg >> 4), value);
+	uint8_t fault = x2apic_write_reg_safe(reg, value);
+
+	__GUEST_ASSERT(!fault, "Unexpected fault 0x%x on WRMSR(%x) = %lx\n",
+		       fault, APIC_BASE_MSR + (reg >> 4), value);
 }
 
+static inline void x2apic_write_reg_fault(unsigned int reg, uint64_t value)
+{
+	uint8_t fault = x2apic_write_reg_safe(reg, value);
+
+	__GUEST_ASSERT(fault == GP_VECTOR,
+		       "Wanted #GP on WRMSR(%x) = %lx, got 0x%x\n",
+		       APIC_BASE_MSR + (reg >> 4), value, fault);
+}
+
+
 #endif /* SELFTEST_KVM_APIC_H */
-- 
2.45.2.1089.g2a221341d9-goog