On Wed, Feb 16, 2022 at 11:37 AM Ben Gardon <bgardon@xxxxxxxxxx> wrote:
>
> On Wed, Feb 2, 2022 at 5:02 PM David Matlack <dmatlack@xxxxxxxxxx> wrote:
> >
> > Separate the code that allocates a new shadow page from the vCPU caches
> > from the code that initializes it. This is in preparation for creating
> > new shadow pages from VM ioctls for eager page splitting, where we do
> > not have access to the vCPU caches.
> >
> > No functional change intended.
> >
> > Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
> > ---
> > arch/x86/kvm/mmu/mmu.c | 44 +++++++++++++++++++++---------------------
> > 1 file changed, 22 insertions(+), 22 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 49f82addf4b5..d4f90a10b652 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -1718,7 +1718,7 @@ static void drop_parent_pte(struct kvm_mmu_page *sp,
> > mmu_spte_clear_no_track(parent_pte);
> > }
> >
> > -static struct kvm_mmu_page *kvm_mmu_alloc_sp(struct kvm_vcpu *vcpu, int direct)
> > +static struct kvm_mmu_page *kvm_mmu_alloc_sp(struct kvm_vcpu *vcpu, bool direct)
> > {
> > struct kvm_mmu_page *sp;
> >
> > @@ -1726,16 +1726,7 @@ static struct kvm_mmu_page *kvm_mmu_alloc_sp(struct kvm_vcpu *vcpu, int direct)
> > sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
> > if (!direct)
> > sp->gfns = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_gfn_array_cache);
> > - set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
>
> I'd be inclined to leave this in the allocation function instead of
> moving it to the init function. It might not be any less code, but if
> you're doing the sp -> page link here, you might as well do the page
> -> sp link too.
Good suggestion. I'll include that change in the next version.
>
> >
> >
> > - /*
> > - * active_mmu_pages must be a FIFO list, as kvm_zap_obsolete_pages()
> > - * depends on valid pages being added to the head of the list. See
> > - * comments in kvm_zap_obsolete_pages().
> > - */
> > - sp->mmu_valid_gen = vcpu->kvm->arch.mmu_valid_gen;
> > - list_add(&sp->link, &vcpu->kvm->arch.active_mmu_pages);
> > - kvm_mod_used_mmu_pages(vcpu->kvm, +1);
> > return sp;
> > }
> >
> > @@ -2144,27 +2135,34 @@ static struct kvm_mmu_page *kvm_mmu_get_existing_sp(struct kvm_vcpu *vcpu,
> > return sp;
> > }
> >
> > -static struct kvm_mmu_page *kvm_mmu_create_sp(struct kvm_vcpu *vcpu,
> > - struct kvm_memory_slot *slot,
> > - gfn_t gfn,
> > - union kvm_mmu_page_role role)
> > +
> > +static void kvm_mmu_init_sp(struct kvm *kvm, struct kvm_mmu_page *sp,
> > + struct kvm_memory_slot *slot, gfn_t gfn,
> > + union kvm_mmu_page_role role)
> > {
> > - struct kvm_mmu_page *sp;
> > struct hlist_head *sp_list;
> >
> > - ++vcpu->kvm->stat.mmu_cache_miss;
> > + ++kvm->stat.mmu_cache_miss;
> > +
> > + set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
> >
> > - sp = kvm_mmu_alloc_sp(vcpu, role.direct);
> > sp->gfn = gfn;
> > sp->role = role;
> > + sp->mmu_valid_gen = kvm->arch.mmu_valid_gen;
> >
> > - sp_list = &vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)];
> > + /*
> > + * active_mmu_pages must be a FIFO list, as kvm_zap_obsolete_pages()
> > + * depends on valid pages being added to the head of the list. See
> > + * comments in kvm_zap_obsolete_pages().
> > + */
> > + list_add(&sp->link, &kvm->arch.active_mmu_pages);
> > + kvm_mod_used_mmu_pages(kvm, 1);
> > +
> > + sp_list = &kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)];
> > hlist_add_head(&sp->hash_link, sp_list);
> >
> > if (!role.direct)
> > - account_shadowed(vcpu->kvm, slot, sp);
> > -
> > - return sp;
> > + account_shadowed(kvm, slot, sp);
> > }
> >
> > static struct kvm_mmu_page *kvm_mmu_get_sp(struct kvm_vcpu *vcpu, gfn_t gfn,
> > @@ -2179,8 +2177,10 @@ static struct kvm_mmu_page *kvm_mmu_get_sp(struct kvm_vcpu *vcpu, gfn_t gfn,
> > goto out;
> >
> > created = true;
> > + sp = kvm_mmu_alloc_sp(vcpu, role.direct);
> > +
> > slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
> > - sp = kvm_mmu_create_sp(vcpu, slot, gfn, role);
> > + kvm_mmu_init_sp(vcpu->kvm, sp, slot, gfn, role);
> >
> > out:
> > trace_kvm_mmu_get_page(sp, created);
> > --
> > 2.35.0.rc2.247.g8bbb082509-goog
> >
