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SubjectRe: [PATCH 15/15] KVM: nVMX: Drop redundant checks on vmcs12 in EPTP switching emulation
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On 10/06/21 01:42, Sean Christopherson wrote:
> Drop the explicit checks on EPTP switching and EPT itself being enabled.
> The EPTP switching check is handled in the generic VMFUNC function check,
> the underlying VMFUNC enablement check is done by hardware and redone
> by generic VMFUNC emulation, and the vmcs12 EPT check is handled by KVM
> at VM-Enter in the form of a consistency check.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/vmx/nested.c | 4 ----
> 1 file changed, 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 0075d3f0f8fa..479ec9378609 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -5448,10 +5448,6 @@ static int nested_vmx_eptp_switching(struct kvm_vcpu *vcpu,
> u32 index = kvm_rcx_read(vcpu);
> u64 new_eptp;
>
> - if (!nested_cpu_has_eptp_switching(vmcs12) ||
> - !nested_cpu_has_ept(vmcs12))
> - return 1;
> -

Perhaps the EPT enabled check is worth keeping with a WARN_ON_ONCE?

Paolo

> if (index >= VMFUNC_EPTP_ENTRIES)
> return 1;
>
>

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