[PATCH v13 45/48] KVM: selftests: Introduce rdmsr_from_l2() and use it for MSR-Bitmap tests

[Vitaly Kuznetsov]

Hyper-V MSR-Bitmap tests do RDMSR from L2 to exit to L1. While 'evmcs_test'
correctly clobbers all GPRs (which are not preserved), 'hyperv_svm_test'
does not. Introduce and use common rdmsr_from_l2() to avoid code
duplication and remove hardcoding of MSRs.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 .../selftests/kvm/include/x86_64/processor.h  |  9 +++++++
 .../testing/selftests/kvm/x86_64/evmcs_test.c | 24 ++++---------------
 .../selftests/kvm/x86_64/hyperv_svm_test.c    |  8 +++----
 3 files changed, 17 insertions(+), 24 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index fbaf0b6cec4b..a14b7e4ea7c4 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -520,6 +520,15 @@ static inline void cpu_relax(void)
 		"hlt\n"	\
 		)
 
+/* Exit to L1 from L2 with RDMSR instruction */
+static inline void rdmsr_from_l2(uint32_t msr)
+{
+	/* Currently, L1 doesn't preserve GPRs during vmexits. */
+	__asm__ __volatile__ ("rdmsr" : : "c"(msr) :
+			      "rax", "rbx", "rdx", "rsi", "rdi", "r8", "r9",
+			      "r10", "r11", "r12", "r13", "r14", "r15");
+}
+
 bool is_intel_cpu(void);
 bool is_amd_cpu(void);
 
diff --git a/tools/testing/selftests/kvm/x86_64/evmcs_test.c b/tools/testing/selftests/kvm/x86_64/evmcs_test.c
index 74f076ba574b..a9f511c192c2 100644
--- a/tools/testing/selftests/kvm/x86_64/evmcs_test.c
+++ b/tools/testing/selftests/kvm/x86_64/evmcs_test.c
@@ -30,22 +30,6 @@ static void guest_nmi_handler(struct ex_regs *regs)
 {
 }
 
-/* Exits to L1 destroy GRPs! */
-static inline void rdmsr_fs_base(void)
-{
-	__asm__ __volatile__ ("mov $0xc0000100, %%rcx; rdmsr" : : :
-			      "rax", "rbx", "rcx", "rdx",
-			      "rsi", "rdi", "r8", "r9", "r10", "r11", "r12",
-			      "r13", "r14", "r15");
-}
-static inline void rdmsr_gs_base(void)
-{
-	__asm__ __volatile__ ("mov $0xc0000101, %%rcx; rdmsr" : : :
-			      "rax", "rbx", "rcx", "rdx",
-			      "rsi", "rdi", "r8", "r9", "r10", "r11", "r12",
-			      "r13", "r14", "r15");
-}
-
 void l2_guest_code(void)
 {
 	GUEST_SYNC(7);
@@ -58,11 +42,11 @@ void l2_guest_code(void)
 	vmcall();
 
 	/* MSR-Bitmap tests */
-	rdmsr_fs_base(); /* intercepted */
-	rdmsr_fs_base(); /* intercepted */
-	rdmsr_gs_base(); /* not intercepted */
+	rdmsr_from_l2(MSR_FS_BASE); /* intercepted */
+	rdmsr_from_l2(MSR_FS_BASE); /* intercepted */
+	rdmsr_from_l2(MSR_GS_BASE); /* not intercepted */
 	vmcall();
-	rdmsr_gs_base(); /* intercepted */
+	rdmsr_from_l2(MSR_GS_BASE); /* intercepted */
 
 	/* Done, exit to L1 and never come back.  */
 	vmcall();
diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_svm_test.c b/tools/testing/selftests/kvm/x86_64/hyperv_svm_test.c
index 1c3fc38b4f15..e30419766c8a 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_svm_test.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_svm_test.c
@@ -30,11 +30,11 @@ void l2_guest_code(void)
 	vmmcall();
 
 	/* MSR-Bitmap tests */
-	rdmsr(MSR_FS_BASE); /* intercepted */
-	rdmsr(MSR_FS_BASE); /* intercepted */
-	rdmsr(MSR_GS_BASE); /* not intercepted */
+	rdmsr_from_l2(MSR_FS_BASE); /* intercepted */
+	rdmsr_from_l2(MSR_FS_BASE); /* intercepted */
+	rdmsr_from_l2(MSR_GS_BASE); /* not intercepted */
 	vmmcall();
-	rdmsr(MSR_GS_BASE); /* intercepted */
+	rdmsr_from_l2(MSR_GS_BASE); /* intercepted */
 
 	GUEST_SYNC(5);
 
-- 
2.37.3