[PATCH v3 12/12] selftests: kvm: Add emulated rdmsr, wrmsr tests

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Add tests to exercise the code paths for em_{rdmsr,wrmsr} and
emulator_{get,set}_msr.  For the generic instruction emulator to work
the module parameter kvm.force_emulation_prefix=1 has to be enabled.  If
it isn't the tests will be skipped.

Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
---

v1 -> v2

 - This commit was added to test the changes made to rdmsr and wrmsr when 
   going through the generic instruction emulator which were made by Alexander
   Graf <graf@xxxxxxxxxx>.

---
 .../selftests/kvm/x86_64/userspace_msr_exit.c | 158 +++++++++++++++++-
 1 file changed, 150 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/userspace_msr_exit.c b/tools/testing/selftests/kvm/x86_64/userspace_msr_exit.c
index 79acfe004e78..04e695eb8ed5 100644
--- a/tools/testing/selftests/kvm/x86_64/userspace_msr_exit.c
+++ b/tools/testing/selftests/kvm/x86_64/userspace_msr_exit.c
@@ -12,8 +12,12 @@
 #include "kvm_util.h"
 #include "vmx.h"
 
-#define VCPU_ID	      1
+/* Forced emulation prefix, used to invoke the emulator unconditionally. */
+#define KVM_FEP "ud2; .byte 'k', 'v', 'm';"
+#define KVM_FEP_LENGTH 5
+static int fep_available = 1;
 
+#define VCPU_ID	      1
 #define MSR_NON_EXISTENT 0x474f4f00
 
 uint32_t msrs[] = {
@@ -63,6 +67,39 @@ static noinline void test_wrmsr(uint32_t msr, uint64_t value)
 extern char rdmsr_start, rdmsr_end;
 extern char wrmsr_start, wrmsr_end;
 
+/*
+ * Note: Force test_em_rdmsr() to not be inlined to prevent the labels,
+ * rdmsr_start and rdmsr_end, from being defined multiple times.
+ */
+static noinline uint64_t test_em_rdmsr(uint32_t msr)
+{
+	uint32_t a, d;
+
+	guest_exception_count = 0;
+
+	__asm__ __volatile__(KVM_FEP "em_rdmsr_start: rdmsr; em_rdmsr_end:" :
+			"=a"(a), "=d"(d) : "c"(msr) : "memory");
+
+	return a | ((uint64_t) d << 32);
+}
+
+/*
+ * Note: Force test_em_wrmsr() to not be inlined to prevent the labels,
+ * wrmsr_start and wrmsr_end, from being defined multiple times.
+ */
+static noinline void test_em_wrmsr(uint32_t msr, uint64_t value)
+{
+	uint32_t a = value;
+	uint32_t d = value >> 32;
+
+	guest_exception_count = 0;
+
+	__asm__ __volatile__(KVM_FEP "em_wrmsr_start: wrmsr; em_wrmsr_end:" ::
+			"a"(a), "d"(d), "c"(msr) : "memory");
+}
+
+extern char em_rdmsr_start, em_rdmsr_end;
+extern char em_wrmsr_start, em_wrmsr_end;
 
 static void guest_code(void)
 {
@@ -112,17 +149,55 @@ static void guest_code(void)
 	GUEST_ASSERT(data == 2);
 	GUEST_ASSERT(guest_exception_count == 0);
 
+	/*
+	 * Test to see if the instruction emulator is available (ie: the module
+	 * parameter 'kvm.force_emulation_prefix=1' is set).  This instruction
+	 * will #UD if it isn't available.
+	 */
+	__asm__ __volatile__(KVM_FEP "nop");
+
+	if (fep_available) {
+		/* Let userspace know we aren't done. */
+		GUEST_SYNC(0);
+
+		/*
+		 * Now run the same tests with the instruction emulator.
+		 */
+		data = test_em_rdmsr(MSR_IA32_XSS);
+		GUEST_ASSERT(data == 0);
+		GUEST_ASSERT(guest_exception_count == 0);
+		test_em_wrmsr(MSR_IA32_XSS, 0);
+		GUEST_ASSERT(guest_exception_count == 0);
+		test_em_wrmsr(MSR_IA32_XSS, 1);
+		GUEST_ASSERT(guest_exception_count == 1);
+
+		test_em_rdmsr(MSR_IA32_FLUSH_CMD);
+		GUEST_ASSERT(guest_exception_count == 1);
+		test_em_wrmsr(MSR_IA32_FLUSH_CMD, 0);
+		GUEST_ASSERT(guest_exception_count == 1);
+		test_em_wrmsr(MSR_IA32_FLUSH_CMD, 1);
+		GUEST_ASSERT(guest_exception_count == 0);
+
+		test_em_wrmsr(MSR_NON_EXISTENT, 2);
+		GUEST_ASSERT(guest_exception_count == 0);
+		data = test_em_rdmsr(MSR_NON_EXISTENT);
+		GUEST_ASSERT(data == 2);
+		GUEST_ASSERT(guest_exception_count == 0);
+	}
+
 	GUEST_DONE();
 }
 
-static void guest_gp_handler(struct ex_regs *regs)
+static void __guest_gp_handler(struct ex_regs *regs,
+			       char *r_start, char *r_end,
+			       char *w_start, char *w_end)
 {
-	if (regs->rip == (uintptr_t)&rdmsr_start) {
-		regs->rip = (uintptr_t)&rdmsr_end;
+	if (regs->rip == (uintptr_t)r_start) {
+		regs->rip = (uintptr_t)r_end;
 		regs->rax = 0;
 		regs->rdx = 0;
-	} else if (regs->rip == (uintptr_t)&wrmsr_start) {
-		regs->rip = (uintptr_t)&wrmsr_end;
+	} else if (regs->rip == (uintptr_t)w_start) {
+		regs->rip = (uintptr_t)w_end;
 	} else {
 		GUEST_ASSERT(!"RIP is at an unknown location!");
 	}
@@ -130,6 +205,24 @@ static void guest_gp_handler(struct ex_regs *regs)
 	++guest_exception_count;
 }
 
+static void guest_gp_handler(struct ex_regs *regs)
+{
+	__guest_gp_handler(regs, &rdmsr_start, &rdmsr_end,
+			   &wrmsr_start, &wrmsr_end);
+}
+
+static void guest_fep_gp_handler(struct ex_regs *regs)
+{
+	__guest_gp_handler(regs, &em_rdmsr_start, &em_rdmsr_end,
+			   &em_wrmsr_start, &em_wrmsr_end);
+}
+
+static void guest_ud_handler(struct ex_regs *regs)
+{
+	fep_available = 0;
+	regs->rip += KVM_FEP_LENGTH;
+}
+
 static void run_guest(struct kvm_vm *vm)
 {
 	int rc;
@@ -225,6 +318,32 @@ static void process_ucall_done(struct kvm_vm *vm)
 		    uc.cmd, UCALL_DONE);
 }
 
+static uint64_t process_ucall(struct kvm_vm *vm)
+{
+	struct kvm_run *run = vcpu_state(vm, VCPU_ID);
+	struct ucall uc = {};
+
+	TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+		    "Unexpected exit reason: %u (%s)",
+		    run->exit_reason,
+		    exit_reason_str(run->exit_reason));
+
+	switch (get_ucall(vm, VCPU_ID, &uc)) {
+	case UCALL_SYNC:
+		break;
+	case UCALL_ABORT:
+		check_for_guest_assert(vm);
+		break;
+	case UCALL_DONE:
+		process_ucall_done(vm);
+		break;
+	default:
+		TEST_ASSERT(false, "Unexpected ucall");
+	}
+
+	return uc.cmd;
+}
+
 static void run_guest_then_process_rdmsr(struct kvm_vm *vm, uint32_t msr_index)
 {
 	run_guest(vm);
@@ -260,7 +379,7 @@ int main(int argc, char *argv[])
 
 	vm_handle_exception(vm, GP_VECTOR, guest_gp_handler);
 
-	/* Process guest code userspace exits */
+	/* Process guest code userspace exits. */
 	run_guest_then_process_rdmsr(vm, MSR_IA32_XSS);
 	run_guest_then_process_wrmsr(vm, MSR_IA32_XSS);
 	run_guest_then_process_wrmsr(vm, MSR_IA32_XSS);
@@ -272,7 +391,30 @@ int main(int argc, char *argv[])
 	run_guest_then_process_wrmsr(vm, MSR_NON_EXISTENT);
 	run_guest_then_process_rdmsr(vm, MSR_NON_EXISTENT);
 
-	run_guest_then_process_ucall_done(vm);
+	vm_handle_exception(vm, UD_VECTOR, guest_ud_handler);
+	run_guest(vm);
+	vm_handle_exception(vm, UD_VECTOR, NULL);
+
+	if (process_ucall(vm) != UCALL_DONE) {
+		vm_handle_exception(vm, GP_VECTOR, guest_fep_gp_handler);
+
+		/* Process emulated rdmsr and wrmsr instructions. */
+		run_guest_then_process_rdmsr(vm, MSR_IA32_XSS);
+		run_guest_then_process_wrmsr(vm, MSR_IA32_XSS);
+		run_guest_then_process_wrmsr(vm, MSR_IA32_XSS);
+
+		run_guest_then_process_rdmsr(vm, MSR_IA32_FLUSH_CMD);
+		run_guest_then_process_wrmsr(vm, MSR_IA32_FLUSH_CMD);
+		run_guest_then_process_wrmsr(vm, MSR_IA32_FLUSH_CMD);
+
+		run_guest_then_process_wrmsr(vm, MSR_NON_EXISTENT);
+		run_guest_then_process_rdmsr(vm, MSR_NON_EXISTENT);
+
+		/* Confirm the guest completed without issues. */
+		run_guest_then_process_ucall_done(vm);
+	} else {
+		printf("To run the instruction emulated tests set the module parameter 'kvm.force_emulation_prefix=1'\n");
+	}
 
 	kvm_vm_free(vm);
 	return 0;
-- 
2.28.0.220.ged08abb693-goog




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