diff options
| author | Vipin Sharma <[email protected]> | 2022-09-21 23:24:51 -0700 |
|---|---|---|
| committer | Sean Christopherson <[email protected]> | 2022-09-28 12:47:19 -0700 |
| commit | dfb45db43e9f6283a79230c8ea9cb589f14791b0 (patch) | |
| tree | 17287a356e4a8301a239b7e1d341c23a03080b4b | |
| parent | bf3f11581893494a5fb01eb87b99627edc2a85ff (diff) | |
KVM: selftests: Load RAX with -EFAULT before Hyper-V hypercall
Load RAX with -EFAULT prior to making a Hyper-V hypercall so that tests
can't get false negatives due to the compiler coincidentally loading the
"right" value into RAX, i.e. to ensure that _KVM_ and not the compiler
is correctly clearing RAX on a successful hypercall.
Note, initializing *hv_status (in C code) to -EFAULT is not sufficient
to avoid false negatives, as the compiler can still "clobber" RAX and
thus load garbage into *hv_status if the hypercall faults (or if KVM
doesn't set RAX).
Suggested-by: Sean Christopherson <[email protected]>
Signed-off-by: Vipin Sharma <[email protected]>
Reviewed-by: Vitaly Kuznetsov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[sean: move to separate patch, massage changelog]
Signed-off-by: Sean Christopherson <[email protected]>
| -rw-r--r-- | tools/testing/selftests/kvm/x86_64/hyperv_features.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c index ad01868548f9..4d55e038c2d7 100644 --- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c +++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c @@ -26,7 +26,8 @@ static inline uint8_t hypercall(u64 control, vm_vaddr_t input_address, : "=a" (*hv_status), "+c" (control), "+d" (input_address), KVM_ASM_SAFE_OUTPUTS(vector) - : [output_address] "r"(output_address) + : [output_address] "r"(output_address), + "a" (-EFAULT) : "cc", "memory", "r8", KVM_ASM_SAFE_CLOBBERS); return vector; } |