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Message-ID: <6744e460e37cdfde3ae28368761da9cc07a61a2e.camel@redhat.com>
Date: Thu, 14 Jul 2022 12:26:07 +0300
From: Maxim Levitsky <mlevitsk@...hat.com>
To: Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <seanjc@...gle.com>
Cc: Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] KVM: selftests: Test Hyper-V invariant TSC control
On Wed, 2022-07-13 at 17:05 +0200, Vitaly Kuznetsov wrote:
> Add a test for the newly introduced Hyper-V invariant TSC control feature:
> - HV_X64_MSR_TSC_INVARIANT_CONTROL is not available without
> HV_ACCESS_TSC_INVARIANT CPUID bit set and available with it.
> - BIT(0) of HV_X64_MSR_TSC_INVARIANT_CONTROL controls the filtering of
> architectural invariant TSC (CPUID.80000007H:EDX[8]) bit.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
> .../selftests/kvm/x86_64/hyperv_features.c | 73 ++++++++++++++++++-
> 1 file changed, 69 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
> index c05acd78548f..9599eecdedff 100644
> --- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c
> +++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
> @@ -15,6 +15,9 @@
>
> #define LINUX_OS_ID ((u64)0x8100 << 48)
>
> +/* CPUID.80000007H:EDX */
> +#define X86_FEATURE_INVTSC (1 << 8)
> +
> static inline uint8_t hypercall(u64 control, vm_vaddr_t input_address,
> vm_vaddr_t output_address, uint64_t *hv_status)
> {
> @@ -60,6 +63,24 @@ static void guest_msr(struct msr_data *msr)
> GUEST_ASSERT_2(!vector, msr->idx, vector);
> else
> GUEST_ASSERT_2(vector == GP_VECTOR, msr->idx, vector);
> +
> + /* Invariant TSC bit appears when TSC invariant control MSR is written to */
> + if (msr->idx == HV_X64_MSR_TSC_INVARIANT_CONTROL) {
> + u32 eax = 0x80000007, ebx = 0, ecx = 0, edx = 0;
> +
> + cpuid(&eax, &ebx, &ecx, &edx);
> +
> + /*
> + * TSC invariant bit is present without the feature (legacy) or
> + * when the feature is present and enabled.
> + */
> + if ((!msr->available && !msr->write) || (msr->write && msr->write_val == 1))
> + GUEST_ASSERT(edx & X86_FEATURE_INVTSC);
> + else
> + GUEST_ASSERT(!(edx & X86_FEATURE_INVTSC));
> + }
> +
> +
> GUEST_DONE();
> }
>
> @@ -105,6 +126,15 @@ static void hv_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
> vcpu_set_cpuid(vcpu, cpuid);
> }
>
> +static bool guest_has_invtsc(void)
> +{
> + struct kvm_cpuid_entry2 *cpuid;
> +
> + cpuid = kvm_get_supported_cpuid_entry(0x80000007);
> +
> + return cpuid->edx & X86_FEATURE_INVTSC;
> +}
> +
> static void guest_test_msrs_access(void)
> {
> struct kvm_vcpu *vcpu;
> @@ -124,6 +154,7 @@ static void guest_test_msrs_access(void)
> struct kvm_cpuid2 *best;
> vm_vaddr_t msr_gva;
> struct msr_data *msr;
> + bool has_invtsc = guest_has_invtsc();
>
> while (true) {
> vm = vm_create_with_one_vcpu(&vcpu, guest_msr);
> @@ -136,8 +167,7 @@ static void guest_test_msrs_access(void)
> vcpu_enable_cap(vcpu, KVM_CAP_HYPERV_ENFORCE_CPUID, 1);
>
> vcpu_set_hv_cpuid(vcpu);
> -
> - best = kvm_get_supported_hv_cpuid();
> + best = vcpu_get_cpuid(vcpu);
>
> vm_init_descriptor_tables(vm);
> vcpu_init_descriptor_tables(vcpu);
> @@ -431,6 +461,42 @@ static void guest_test_msrs_access(void)
> break;
>
> case 44:
> + /* MSR is not available when CPUID feature bit is unset */
> + if (!has_invtsc)
> + continue;
> + msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
> + msr->write = 0;
> + msr->available = 0;
> + break;
> + case 45:
> + /* MSR is vailable when CPUID feature bit is set */
> + if (!has_invtsc)
> + continue;
> + feat.eax |= HV_ACCESS_TSC_INVARIANT;
> + msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
> + msr->write = 0;
> + msr->available = 1;
> + break;
> + case 46:
> + /* Writing bits other than 0 is forbidden */
> + if (!has_invtsc)
> + continue;
> + msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
> + msr->write = 1;
> + msr->write_val = 0xdeadbeef;
> + msr->available = 0;
> + break;
> + case 47:
> + /* Setting bit 0 enables the feature */
> + if (!has_invtsc)
> + continue;
> + msr->idx = HV_X64_MSR_TSC_INVARIANT_CONTROL;
> + msr->write = 1;
> + msr->write_val = 1;
> + msr->available = 1;
> + break;
> +
> + default:
> kvm_vm_free(vm);
> return;
> }
> @@ -502,8 +568,7 @@ static void guest_test_hcalls_access(void)
> vcpu_enable_cap(vcpu, KVM_CAP_HYPERV_ENFORCE_CPUID, 1);
>
> vcpu_set_hv_cpuid(vcpu);
> -
> - best = kvm_get_supported_hv_cpuid();
> + best = vcpu_get_cpuid(vcpu);
>
> run = vcpu->run;
>
Tiny unrelated nitpick: 'msr->available' is misleading, it is more like
'msr->should_not_gp' or something - might be worth it to refactor in the future.
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
Best regards,
Maxim Levitsky
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