Re: [PATCH v2 07/49] KVM: selftests: Verify KVM stuffs runtime CPUID OS bits on CR4 writes
From: Maxim Levitsky
Date: Thu Jul 04 2024 - 21:02:43 EST
On Fri, 2024-05-17 at 10:38 -0700, Sean Christopherson wrote:
> Extend x86's set sregs test to verify that KVM sets/clears OSXSAVE and
> OSKPKE according to CR4.XSAVE and CR4.PKE respectively. For performance
> reasons, KVM is responsible for emulating the architectural behavior of
> the OS CPUID bits tracking CR4.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> tools/testing/selftests/kvm/x86_64/set_sregs_test.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/set_sregs_test.c b/tools/testing/selftests/kvm/x86_64/set_sregs_test.c
> index 96fd690d479a..f4095a3d1278 100644
> --- a/tools/testing/selftests/kvm/x86_64/set_sregs_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/set_sregs_test.c
> @@ -85,6 +85,16 @@ static void test_cr_bits(struct kvm_vcpu *vcpu, uint64_t cr4)
> rc = _vcpu_sregs_set(vcpu, &sregs);
> TEST_ASSERT(!rc, "Failed to set supported CR4 bits (0x%lx)", cr4);
>
> + TEST_ASSERT(!!(sregs.cr4 & X86_CR4_OSXSAVE) ==
> + (vcpu->cpuid && vcpu_cpuid_has(vcpu, X86_FEATURE_OSXSAVE)),
> + "KVM didn't %s OSXSAVE in CPUID as expected",
> + (sregs.cr4 & X86_CR4_OSXSAVE) ? "set" : "clear");
> +
> + TEST_ASSERT(!!(sregs.cr4 & X86_CR4_PKE) ==
> + (vcpu->cpuid && vcpu_cpuid_has(vcpu, X86_FEATURE_OSPKE)),
> + "KVM didn't %s OSPKE in CPUID as expected",
> + (sregs.cr4 & X86_CR4_PKE) ? "set" : "clear");
> +
Hi,
Just for fun, why not to have a test function that toggles a CR4 bit and then
checks the corresponding CPUID bit toggles as well? This is both better
coverage wise and will remove the above code duplication.
Best regards,
Maxim Levitsky
> vcpu_sregs_get(vcpu, &sregs);
> TEST_ASSERT(sregs.cr4 == cr4, "sregs.CR4 (0x%llx) != CR4 (0x%lx)",
> sregs.cr4, cr4);