Re: [PATCH v5 03/21] KVM: x86/mmu: Derive shadow MMU page role from parent

David Matlack
2022-05-16T21:38:53Z

On Sun, May 15, 2022 at 11:55 PM Lai Jiangshan <jiangshanlai@gmail.com> wrote:
>
> On Sat, May 14, 2022 at 4:28 AM David Matlack <dmatlack@google.com> wrote:
>
> > -static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, gva_t gva,
> > +static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant,
> > u8 level, bool direct)
> > {
> > + union kvm_mmu_page_role role;
> > struct kvm_mmu_page *sp;
> >
> > - sp = kvm_mmu_get_page(vcpu, gfn, gva, level, direct, ACC_ALL);
> > + role = vcpu->arch.mmu->root_role;
> > + role.level = level;
> > + role.direct = direct;
> > + role.access = ACC_ALL;
> > +
> > + if (role.has_4_byte_gpte)
> > + role.quadrant = quadrant;
> > +
> > + if (level <= vcpu->arch.mmu->cpu_role.base.level)
> > + role.passthrough = 0;
> > +
>
>
>
> + role.level = level;
> +
> + if (role.has_4_byte_gpte)
> + role.quadrant = quadrant;
>
> Only these lines are needed because of mmu->pae_root, others are
> the same as vcpu->arch.mmu->root_role.
>
> The argument @direct is vcpu->arch.mmu->root_role.direct.
> vcpu->arch.mmu->root_role.access is always set to be ACC_ALL.
>
> vcpu->arch.mmu->root_role.passthrough is 0 when mmu->pae_root is used.
> Or if vcpu->arch.mmu->root_role.passthrough is 1, @level must be 5
> and vcpu->arch.mmu->cpu_role.base.level must be 4, the code here
> is useless.

Ah, thank you for the tip. That is cleaner.