Re: [PATCH v2 2/3] KVM: x86: Handle the case of 5-level shadow page table

Wei Huang
2021-08-09T17:03:52Z

On 8/9/21 10:17 AM, Sean Christopherson wrote:
> On Sun, Aug 08, 2021, Wei Huang wrote:
>> @@ -3457,10 +3457,19 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
>> mmu->pae_root[i] = root | pm_mask;
>> }
>>
>> - if (mmu->shadow_root_level == PT64_ROOT_4LEVEL)
>> + /*
>> + * Depending on the shadow_root_level, build the root_hpa table by
>> + * chaining either pml5->pml4->pae or pml4->pae.
>> + */
>> + mmu->root_hpa = __pa(mmu->pae_root);
>> + if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL) {
>> + mmu->pml4_root[0] = mmu->root_hpa | pm_mask;
>> mmu->root_hpa = __pa(mmu->pml4_root);
>> - else
>> - mmu->root_hpa = __pa(mmu->pae_root);
>> + }
>> + if (mmu->shadow_root_level == PT64_ROOT_5LEVEL) {
>> + mmu->pml5_root[0] = mmu->root_hpa | pm_mask;
>> + mmu->root_hpa = __pa(mmu->pml5_root);
>> + }
>
> I still really dislike this approach, it requires visually connecting multiple
> statements to understand the chain. I don't see any advantage (the 6-level paging
> comment was 99.9% a joke) of rewriting root_hpa other than that's how it's done today.
>

I can change this part in v3, unless different comments from other
reviewers.

> In the future, please give reviewers ample opportunity to respond before sending
> a new version if there's disagreement, otherwise the conversation gets carried
> over into a different thread and loses the original context.
>
>>
>> set_root_pgd:
>> mmu->root_pgd = root_pgd;