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
