Re: [RFC PATCH V3 3/4] KVM: X86: Alloc role.pae_root shadow page

[Paolo Bonzini]

On 4/14/22 11:07, Lai Jiangshan wrote:
> > I don't think this will work for shadow paging.  CR3 only has to be 32-byte aligned
> > for PAE paging.  Unless I'm missing something subtle in the code, KVM will incorrectly
> > reuse a pae_root if the guest puts multiple PAE CR3s on a single page because KVM's
> > gfn calculation will drop bits 11:5.
>
> I forgot about it.


Isn't the pae_root always rebuilt by

        if (!tdp_enabled && memcmp(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs)))
                kvm_mmu_free_roots(vcpu->kvm, mmu, KVM_MMU_ROOT_CURRENT);

in load_pdptrs?  I think reuse cannot happen.

Paolo