On Thu, 2022-07-14 at 11:13 +0200, Vitaly Kuznetsov wrote:
> KVM has to check guest visible HYPERV_CPUID_NESTED_FEATURES.EBX CPUID
> leaf to know which Enlightened VMCS definition to use (original or 2022
> update). Cache the leaf along with other Hyper-V CPUID feature leaves
> to make the check quick.
>
> While on it, wipe the whole 'hv_vcpu->cpuid_cache' with memset() instead
> of having to zero each particular member when the corresponding CPUID entry
> was not found.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/hyperv.c | 17 ++++++++---------
> 2 files changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index de5a149d0971..077ec9cf3169 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -616,6 +616,8 @@ struct kvm_vcpu_hv {
> u32 enlightenments_eax; /* HYPERV_CPUID_ENLIGHTMENT_INFO.EAX */
> u32 enlightenments_ebx; /* HYPERV_CPUID_ENLIGHTMENT_INFO.EBX */
> u32 syndbg_cap_eax; /* HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES.EAX */
> + u32 nested_eax; /* HYPERV_CPUID_NESTED_FEATURES.EAX */
> + u32 nested_ebx; /* HYPERV_CPUID_NESTED_FEATURES.EBX */
> } cpuid_cache;
> };
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index e08189211d9a..a8e4944ca110 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -2005,31 +2005,30 @@ void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu)
>
> hv_vcpu = to_hv_vcpu(vcpu);
>
> + memset(&hv_vcpu->cpuid_cache, 0, sizeof(hv_vcpu->cpuid_cache));
> +
> entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_FEATURES, 0);
> if (entry) {
> hv_vcpu->cpuid_cache.features_eax = entry->eax;
> hv_vcpu->cpuid_cache.features_ebx = entry->ebx;
> hv_vcpu->cpuid_cache.features_edx = entry->edx;
> - } else {
> - hv_vcpu->cpuid_cache.features_eax = 0;
> - hv_vcpu->cpuid_cache.features_ebx = 0;
> - hv_vcpu->cpuid_cache.features_edx = 0;
> }
>
> entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_ENLIGHTMENT_INFO, 0);
> if (entry) {
> hv_vcpu->cpuid_cache.enlightenments_eax = entry->eax;
> hv_vcpu->cpuid_cache.enlightenments_ebx = entry->ebx;
> - } else {
> - hv_vcpu->cpuid_cache.enlightenments_eax = 0;
> - hv_vcpu->cpuid_cache.enlightenments_ebx = 0;
> }
>
> entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES, 0);
> if (entry)
> hv_vcpu->cpuid_cache.syndbg_cap_eax = entry->eax;
> - else
> - hv_vcpu->cpuid_cache.syndbg_cap_eax = 0;
> +
> + entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_NESTED_FEATURES, 0);
> + if (entry) {
> + hv_vcpu->cpuid_cache.nested_eax = entry->eax;
> + hv_vcpu->cpuid_cache.nested_ebx = entry->ebx;
> + }
> }
>
> int kvm_hv_set_enforce_cpuid(struct kvm_vcpu *vcpu, bool enforce)
Makes sense, looks good.
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
