KVM: selftests: Introduce rdmsr_from_l2() and use it for MSR-Bitmap t…

…ests 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 a more generic rdmsr_from_l2() to avoid code duplication and remove hardcoding of MSRs. Do not put it in common code because it is really just a selftests bug rather than a processor feature that requires it. Signed-off-by: Vitaly Kuznetsov <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]> Message-Id: <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]>
josf · Nov 21, 2022 · 75ee750 · 75ee750
1 parent 8fda37c
commit 75ee750
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Showing 2 changed files with 23 additions and 21 deletions.
diff --git a/tools/testing/selftests/kvm/x86_64/evmcs_test.c b/tools/testing/selftests/kvm/x86_64/evmcs_test.c
@@ -30,22 +30,15 @@ static void guest_nmi_handler(struct ex_regs *regs)
 {
 }
 
-/* Exits to L1 destroy GRPs! */
-static inline void rdmsr_fs_base(void)
+static inline void rdmsr_from_l2(uint32_t msr)
 {
-	__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");
+	/* 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");
 }
 
+/* Exit to L1 from L2 with RDMSR instruction */
 void l2_guest_code(void)
 {
 	GUEST_SYNC(7);
@@ -58,11 +51,11 @@ 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
@@ -23,18 +23,27 @@
 
 #define L2_GUEST_STACK_SIZE 256
 
+/* 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");
+}
+
 void l2_guest_code(void)
 {
 	GUEST_SYNC(3);
 	/* Exit to L1 */
 	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);