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[34.82.80.254]) by smtp.gmail.com with ESMTPSA id j15-20020a170903024f00b0015eee3ab203sm9562937plh.49.2022.05.17.09.42.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 May 2022 09:42:03 -0700 (PDT) Date: Tue, 17 May 2022 16:41:59 +0000 From: David Matlack To: Lai Jiangshan Cc: LKML , "open list:KERNEL VIRTUAL MACHINE FOR MIPS (KVM/mips)" , Paolo Bonzini , Sean Christopherson , Lai Jiangshan , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , X86 ML , "H. Peter Anvin" Subject: Re: [PATCH V2 3/7] KVM: X86/MMU: Link PAE root pagetable with its children Message-ID: References: <20220503150735.32723-1-jiangshanlai@gmail.com> <20220503150735.32723-4-jiangshanlai@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, May 17, 2022 at 09:13:54AM +0800, Lai Jiangshan wrote: > On Tue, May 17, 2022 at 8:01 AM David Matlack wrote: > > > > On Tue, May 03, 2022 at 11:07:31PM +0800, Lai Jiangshan wrote: > > > From: Lai Jiangshan > > > > > > When special shadow pages are activated, link_shadow_page() might link > > > a special shadow pages which is the PAE root for PAE paging with its > > > children. > > > > > > Add make_pae_pdpte() to handle it. > > > > > > The code is not activated since special shadow pages are not activated > > > yet. > > > > > > Signed-off-by: Lai Jiangshan > > > --- > > > arch/x86/kvm/mmu/mmu.c | 6 +++++- > > > arch/x86/kvm/mmu/spte.c | 7 +++++++ > > > arch/x86/kvm/mmu/spte.h | 1 + > > > 3 files changed, 13 insertions(+), 1 deletion(-) > > > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > > index 126f0cd07f98..3fe70ad3bda2 100644 > > > --- a/arch/x86/kvm/mmu/mmu.c > > > +++ b/arch/x86/kvm/mmu/mmu.c > > > @@ -2277,7 +2277,11 @@ static void link_shadow_page(struct kvm_vcpu *vcpu, u64 *sptep, > > > > > > BUILD_BUG_ON(VMX_EPT_WRITABLE_MASK != PT_WRITABLE_MASK); > > > > > > - spte = make_nonleaf_spte(sp->spt, sp_ad_disabled(sp)); > > > + if (unlikely(sp->role.level == PT32_ROOT_LEVEL && > > > + vcpu->arch.mmu->root_role.level == PT32E_ROOT_LEVEL)) > > > + spte = make_pae_pdpte(sp->spt); > > > + else > > > + spte = make_nonleaf_spte(sp->spt, sp_ad_disabled(sp)); > > > > > > mmu_spte_set(sptep, spte); > > > > > > diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c > > > index 75c9e87d446a..ccd9267a58ca 100644 > > > --- a/arch/x86/kvm/mmu/spte.c > > > +++ b/arch/x86/kvm/mmu/spte.c > > > @@ -251,6 +251,13 @@ u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index) > > > return child_spte; > > > } > > > > > > +u64 make_pae_pdpte(u64 *child_pt) > > > +{ > > > + /* The only ignore bits in PDPTE are 11:9. */ > > > + BUILD_BUG_ON(!(GENMASK(11,9) & SPTE_MMU_PRESENT_MASK)); > > > + return __pa(child_pt) | PT_PRESENT_MASK | SPTE_MMU_PRESENT_MASK | > > > + shadow_me_value; > > > > If I'm reading mmu_alloc_{direct,shadow}_roots() correctly, PAE page > > directories just get: root | PT_PRESENT_MASK | shadow_me_value. Is there > > a reason to add SPTE_MMU_PRESENT_MASK or am I misreading the code? > > Because it has a struct kvm_mmu_page associated with it now. > > sp->spt[i] requires SPTE_MMU_PRESENT_MASK if it is present. Ah of course. e.g. FNAME(fetch) will call is_shadow_present_pte() on PAE PDPTEs. Could you also update the comment above SPTE_MMU_PRESENT_MASK? Right now it says: "Use bit 11, as it is ignored by all flavors of SPTEs and checking a low bit often generates better code than for a high bit, e.g. 56+." I think it would be helpful to also meniton that SPTE_MMU_PRESENT_MASK is also used in PDPTEs which only ignore bits 11:9. > > > > > > +} > > > > > > u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled) > > > { > > > diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h > > > index fbbab180395e..09a7e4ba017a 100644 > > > --- a/arch/x86/kvm/mmu/spte.h > > > +++ b/arch/x86/kvm/mmu/spte.h > > > @@ -413,6 +413,7 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, > > > u64 old_spte, bool prefetch, bool can_unsync, > > > bool host_writable, u64 *new_spte); > > > u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index); > > > +u64 make_pae_pdpte(u64 *child_pt); > > > u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled); > > > u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access); > > > u64 mark_spte_for_access_track(u64 spte); > > > -- > > > 2.19.1.6.gb485710b > > >