[kvm-unit-tests PATCH 04/14] x86: msr: Restore original MSR value after writing arbitrary test value

Sean Christopherson
2021-04-22T03:05:21Z

Restore the original MSR value after the WRMSR/RDMSR test. MSR_GS_BASE
in particular needs to be restored as it points at per-cpu data.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
x86/msr.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/x86/msr.c b/x86/msr.c
index 757156d..5a3f1c3 100644
--- a/x86/msr.c
+++ b/x86/msr.c
@@ -77,7 +77,7 @@ static int find_msr_info(int msr_index)

static void test_msr_rw(int msr_index, unsigned long long input, unsigned long long expected)
{
- unsigned long long r = 0;
+ unsigned long long r, orig;
int index;
const char *sptr;
if ((index = find_msr_info(msr_index)) != -1) {
@@ -86,8 +86,11 @@ static void test_msr_rw(int msr_index, unsigned long long input, unsigned long l
printf("couldn't find name for msr # %#x, skipping\n", msr_index);
return;
}
+
+ orig = rdmsr(msr_index);
wrmsr(msr_index, input);
r = rdmsr(msr_index);
+ wrmsr(msr_index, orig);
if (expected != r) {
printf("testing %s: output = %#" PRIx32 ":%#" PRIx32
" expected = %#" PRIx32 ":%#" PRIx32 "\n", sptr,