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SubjectRe: [PATCH v1 3/4] KVM: MMU: Add 5 level EPT & Shadow page table support.
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On 12/08/2017 15:35, Yu Zhang wrote:
> struct rsvd_bits_validate {
> - u64 rsvd_bits_mask[2][4];
> + u64 rsvd_bits_mask[2][5];
> u64 bad_mt_xwr;
> };


Can you change this 4 to PT64_ROOT_MAX_LEVEL in patch 2?

> - if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_4LEVEL &&
> - (vcpu->arch.mmu.root_level == PT64_ROOT_4LEVEL ||
> - vcpu->arch.mmu.direct_map)) {
> + if (vcpu->arch.mmu.root_level >= PT64_ROOT_4LEVEL ||
> + vcpu->arch.mmu.direct_map) {
> hpa_t root = vcpu->arch.mmu.root_hpa;

You should keep the check on shadow_root_level (changing it to >= of
course), otherwise you break the case where EPT is disabled, paging is
disabled (so vcpu->arch.mmu.direct_map is true) and the host kernel is
32-bit. In that case shadow pages use PAE format, and entering this
branch is incorrect.

> @@ -4444,7 +4457,7 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
>
> MMU_WARN_ON(VALID_PAGE(context->root_hpa));
>
> - context->shadow_root_level = kvm_x86_ops->get_tdp_level();
> + context->shadow_root_level = kvm_x86_ops->get_tdp_level(vcpu);
>
> context->nx = true;
> context->ept_ad = accessed_dirty;

Below, there is:

context->root_level = context->shadow_root_level;

this should be forced to PT64_ROOT_4LEVEL until there is support for
nested EPT 5-level page tables.

Thanks,

Paolo

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