Re: [PATCH v11 30/35] KVM: x86: Add gmem hook for determining max NPT mapping level

Michael Roth
2024-02-12T17:03:56Z

On Mon, Feb 12, 2024 at 11:50:26AM +0100, Paolo Bonzini wrote:
> On Sat, Dec 30, 2023 at 6:32 PM Michael Roth <michael.roth@amd.com> wrote:
> > int max_order, r;
> > + u8 max_level;
> >
> > if (!kvm_slot_can_be_private(fault->slot)) {
> > kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
> > @@ -4321,8 +4322,15 @@ static int kvm_faultin_pfn_private(struct kvm_vcpu *vcpu,
> > return r;
> > }
> >
> > - fault->max_level = min(kvm_max_level_for_order(max_order),
> > - fault->max_level);
> > + max_level = kvm_max_level_for_order(max_order);
> > + r = static_call(kvm_x86_gmem_max_level)(vcpu->kvm, fault->pfn,
> > + fault->gfn, &max_level);
>
> Might as well pass &fault->max_level directly to the callback, with no
> change to the vendor-specific code.
>
> I'll include the MMU part in a generic series to be the base for both
> Intel TDX and AMD SEV-SNP, and will do that change.

Sounds good. I'm not sure why I did it that way originally, but what
you're suggesting does seem like it should be equivalent.

-Mike

>
> Paolo
>
> > + if (r) {
> > + kvm_release_pfn_clean(fault->pfn);
> > + return r;
> > + }
> > +
> > + fault->max_level = min(max_level, fault->max_level);
> > fault->map_writable = !(fault->slot->flags & KVM_MEM_READONLY);
> >
> > return RET_PF_CONTINUE;
> > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > index 85f63b6842b6..5eb836b73131 100644
> > --- a/arch/x86/kvm/svm/sev.c
> > +++ b/arch/x86/kvm/svm/sev.c
> > @@ -4315,3 +4315,30 @@ void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end)
> > pfn += use_2m_update ? PTRS_PER_PMD : 1;
> > }
> > }
> > +
> > +int sev_gmem_max_level(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, u8 *max_level)
> > +{
> > + int level, rc;
> > + bool assigned;
> > +
> > + if (!sev_snp_guest(kvm))
> > + return 0;
> > +
> > + rc = snp_lookup_rmpentry(pfn, &assigned, &level);
> > + if (rc) {
> > + pr_err_ratelimited("SEV: RMP entry not found: GFN %llx PFN %llx level %d error %d\n",
> > + gfn, pfn, level, rc);
> > + return -ENOENT;
> > + }
> > +
> > + if (!assigned) {
> > + pr_err_ratelimited("SEV: RMP entry is not assigned: GFN %llx PFN %llx level %d\n",
> > + gfn, pfn, level);
> > + return -EINVAL;
> > + }
> > +
> > + if (level < *max_level)
> > + *max_level = level;
> > +
> > + return 0;
> > +}
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index f26b8c2a8be4..f745022f7454 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -5067,6 +5067,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
> > .alloc_apic_backing_page = svm_alloc_apic_backing_page,
> >
> > .gmem_prepare = sev_gmem_prepare,
> > + .gmem_max_level = sev_gmem_max_level,
> > .gmem_invalidate = sev_gmem_invalidate,
> > };
> >
> > --
> > 2.25.1
> >
>