On Sat, Nov 20, 2021 at 4:53 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 11/20/21 00:57, David Matlack wrote:
> > Derive the page role from the parent shadow page, since the only thing
> > that changes is the level. This is in preparation for eagerly splitting
> > large pages during VM-ioctls which does not have access to the vCPU
> > MMU context.
> >
> > No functional change intended.
> >
> > Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
> > ---
> > arch/x86/kvm/mmu/tdp_mmu.c | 43 ++++++++++++++++++++------------------
> > 1 file changed, 23 insertions(+), 20 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> > index b70707a7fe87..1a409992a57f 100644
> > --- a/arch/x86/kvm/mmu/tdp_mmu.c
> > +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> > @@ -157,23 +157,8 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
> > if (kvm_mmu_page_as_id(_root) != _as_id) { \
> > } else
> >
> > -static union kvm_mmu_page_role page_role_for_level(struct kvm_vcpu *vcpu,
> > - int level)
> > -{
> > - union kvm_mmu_page_role role;
> > -
> > - role = vcpu->arch.mmu->mmu_role.base;
> > - role.level = level;
> > - role.direct = true;
> > - role.gpte_is_8_bytes = true;
> > - role.access = ACC_ALL;
> > - role.ad_disabled = !shadow_accessed_mask;
> > -
> > - return role;
> > -}
> > -
> > static struct kvm_mmu_page *alloc_tdp_mmu_page(struct kvm_vcpu *vcpu, gfn_t gfn,
> > - int level)
> > + union kvm_mmu_page_role role)
> > {
> > struct kvm_mmu_memory_caches *mmu_caches;
> > struct kvm_mmu_page *sp;
> > @@ -184,7 +169,7 @@ static struct kvm_mmu_page *alloc_tdp_mmu_page(struct kvm_vcpu *vcpu, gfn_t gfn,
> > sp->spt = kvm_mmu_memory_cache_alloc(&mmu_caches->shadow_page_cache);
> > set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
> >
> > - sp->role.word = page_role_for_level(vcpu, level).word;
> > + sp->role = role;
> > sp->gfn = gfn;
> > sp->tdp_mmu_page = true;
> >
> > @@ -193,6 +178,19 @@ static struct kvm_mmu_page *alloc_tdp_mmu_page(struct kvm_vcpu *vcpu, gfn_t gfn,
> > return sp;
> > }
> >
> > +static struct kvm_mmu_page *alloc_child_tdp_mmu_page(struct kvm_vcpu *vcpu, struct tdp_iter *iter)
> > +{
> > + struct kvm_mmu_page *parent_sp;
> > + union kvm_mmu_page_role role;
> > +
> > + parent_sp = sptep_to_sp(rcu_dereference(iter->sptep));
> > +
> > + role = parent_sp->role;
> > + role.level--;
> > +
> > + return alloc_tdp_mmu_page(vcpu, iter->gfn, role);
> > +}
> > +
> > hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
> > {
> > union kvm_mmu_page_role role;
> > @@ -201,7 +199,12 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
> >
> > lockdep_assert_held_write(&kvm->mmu_lock);
> >
> > - role = page_role_for_level(vcpu, vcpu->arch.mmu->shadow_root_level);
> > + role = vcpu->arch.mmu->mmu_role.base;
> > + role.level = vcpu->arch.mmu->shadow_root_level;
> > + role.direct = true;
> > + role.gpte_is_8_bytes = true;
> > + role.access = ACC_ALL;
> > + role.ad_disabled = !shadow_accessed_mask;
>
> I have a similar patch for the old MMU, but it was also replacing
> shadow_root_level with shadow_root_role. I'll see if I can adapt it to
> the TDP MMU, since the shadow_root_role is obviously the same for both.
While I was writing this patch it got me wondering if we can do an
even more general refactor and replace root_hpa and shadow_root_level
with a pointer to the root kvm_mmu_page struct. But I didn't get a
chance to look into it further.
>
> Paolo
>
> > /* Check for an existing root before allocating a new one. */
> > for_each_tdp_mmu_root(kvm, root, kvm_mmu_role_as_id(role)) {
> > @@ -210,7 +213,7 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
> > goto out;
> > }
> >
> > - root = alloc_tdp_mmu_page(vcpu, 0, vcpu->arch.mmu->shadow_root_level);
> > + root = alloc_tdp_mmu_page(vcpu, 0, role);
> > refcount_set(&root->tdp_mmu_root_count, 1);
> >
> > spin_lock(&kvm->arch.tdp_mmu_pages_lock);
> > @@ -1028,7 +1031,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> > if (is_removed_spte(iter.old_spte))
> > break;
> >
> > - sp = alloc_tdp_mmu_page(vcpu, iter.gfn, iter.level - 1);
> > + sp = alloc_child_tdp_mmu_page(vcpu, &iter);
> > if (!tdp_mmu_install_sp_atomic(vcpu->kvm, &iter, sp, account_nx))
> > break;
> > }
> >
