[Patch v3 06/13] KVM: selftests: Test that values written to Hyper-V MSRs are preserved

Vipin Sharma
2022-12-05T19:15:50Z

From: Vitaly Kuznetsov <vkuznets@redhat.com>

Enhance 'hyperv_features' selftest by adding a check that KVM
preserves values written to PV MSRs. Two MSRs are, however, 'special':
- HV_X64_MSR_EOI as it is a 'write-only' MSR,
- HV_X64_MSR_RESET as it always reads as '0'.
The later doesn't require any special handling right now because the
test never writes anything besides '0' to the MSR, leave a TODO node
about the fact.

Suggested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
.../selftests/kvm/x86_64/hyperv_features.c | 36 ++++++++++++++-----
1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
index daad3e3cc7bb..b00240963974 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
@@ -34,22 +34,36 @@ struct hcall_data {
bool ud_expected;
};

+static bool is_write_only_msr(uint32_t msr)
+{
+ return msr == HV_X64_MSR_EOI;
+}
+
static void guest_msr(struct msr_data *msr)
{
- uint64_t ignored;
- uint8_t vector;
+ uint8_t vector = 0;
+ uint64_t msr_val = 0;

GUEST_ASSERT(msr->idx);

- if (!msr->write)
- vector = rdmsr_safe(msr->idx, &ignored);
- else
+ if (msr->write)
vector = wrmsr_safe(msr->idx, msr->write_val);

+ if (!vector && (!msr->write || !is_write_only_msr(msr->idx)))
+ vector = rdmsr_safe(msr->idx, &msr_val);
+
if (msr->fault_expected)
- GUEST_ASSERT_2(vector == GP_VECTOR, msr->idx, vector);
+ GUEST_ASSERT_3(vector == GP_VECTOR, msr->idx, vector, GP_VECTOR);
else
- GUEST_ASSERT_2(!vector, msr->idx, vector);
+ GUEST_ASSERT_3(!vector, msr->idx, vector, 0);
+
+ if (vector || is_write_only_msr(msr->idx))
+ goto done;
+
+ if (msr->write)
+ GUEST_ASSERT_3(msr_val == msr->write_val, msr->idx,
+ msr_val, msr->write_val);
+done:
GUEST_DONE();
}

@@ -239,6 +253,12 @@ static void guest_test_msrs_access(void)
case 16:
msr->idx = HV_X64_MSR_RESET;
msr->write = true;
+ /*
+ * TODO: the test only writes '0' to HV_X64_MSR_RESET
+ * at the moment, writing some other value there will
+ * trigger real vCPU reset and the code is not prepared
+ * to handle it yet.
+ */
msr->write_val = 0;
msr->fault_expected = false;
break;
@@ -433,7 +453,7 @@ static void guest_test_msrs_access(void)

switch (get_ucall(vcpu, &uc)) {
case UCALL_ABORT:
- REPORT_GUEST_ASSERT_2(uc, "MSR = %lx, vector = %lx");
+ REPORT_GUEST_ASSERT_3(uc, "MSR = %lx, arg1 = %lx, arg2 = %lx");
return;