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Mon, 09 Sep 2024 06:51:41 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEDfIgsMO6NLNmoe2gXmS+oP/AsxfqL24bcUlxSPiMg6y6PqpLe7sOx2QTJodRnKO68Qy7p9g== X-Received: by 2002:adf:e84a:0:b0:374:c92e:f69f with SMTP id ffacd0b85a97d-378895caf24mr7229033f8f.16.1725889900970; Mon, 09 Sep 2024 06:51:40 -0700 (PDT) Received: from [192.168.10.81] ([151.95.101.29]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-378956650fdsm6120284f8f.25.2024.09.09.06.51.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Sep 2024 06:51:40 -0700 (PDT) Message-ID: Date: Mon, 9 Sep 2024 15:51:39 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/21] KVM: x86/tdp_mmu: Add a helper function to walk down the TDP MMU To: Rick Edgecombe , seanjc@google.com, kvm@vger.kernel.org Cc: kai.huang@intel.com, dmatlack@google.com, isaku.yamahata@gmail.com, yan.y.zhao@intel.com, nik.borisov@suse.com, linux-kernel@vger.kernel.org References: <20240904030751.117579-1-rick.p.edgecombe@intel.com> <20240904030751.117579-3-rick.p.edgecombe@intel.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/4/24 05:07, Rick Edgecombe wrote: > From: Isaku Yamahata > > Export a function to walk down the TDP without modifying it and simply > check if a PGA is mapped. > > Future changes will support pre-populating TDX private memory. In order to > implement this KVM will need to check if a given GFN is already > pre-populated in the mirrored EPT. [1] > > There is already a TDP MMU walker, kvm_tdp_mmu_get_walk() for use within > the KVM MMU that almost does what is required. However, to make sense of > the results, MMU internal PTE helpers are needed. Refactor the code to > provide a helper that can be used outside of the KVM MMU code. > > Refactoring the KVM page fault handler to support this lookup usage was > also considered, but it was an awkward fit. > > kvm_tdp_mmu_gpa_is_mapped() is based on a diff by Paolo Bonzini. > > Link: https://lore.kernel.org/kvm/ZfBkle1eZFfjPI8l@google.com/ [1] > Signed-off-by: Isaku Yamahata > Co-developed-by: Rick Edgecombe > Signed-off-by: Rick Edgecombe > --- > TDX MMU part 2 v1: > - Change exported function to just return of GPA is mapped because "You > are executing with the filemap_invalidate_lock() taken, and therefore > cannot race with kvm_gmem_punch_hole()" (Paolo) > https://lore.kernel.org/kvm/CABgObfbpNN842noAe77WYvgi5MzK2SAA_FYw-=fGa+PcT_Z22w@mail.gmail.com/ > - Take root hpa instead of enum (Paolo) > > TDX MMU Prep v2: > - Rename function with "mirror" and use root enum > > TDX MMU Prep: > - New patch > --- > arch/x86/kvm/mmu.h | 3 +++ > arch/x86/kvm/mmu/mmu.c | 3 +-- > arch/x86/kvm/mmu/tdp_mmu.c | 37 ++++++++++++++++++++++++++++++++----- > 3 files changed, 36 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h > index 8f289222b353..5faa416ac874 100644 > --- a/arch/x86/kvm/mmu.h > +++ b/arch/x86/kvm/mmu.h > @@ -254,6 +254,9 @@ extern bool tdp_mmu_enabled; > #define tdp_mmu_enabled false > #endif > > +bool kvm_tdp_mmu_gpa_is_mapped(struct kvm_vcpu *vcpu, u64 gpa); > +int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, u8 *level); > + > static inline bool kvm_memslots_have_rmaps(struct kvm *kvm) > { > return !tdp_mmu_enabled || kvm_shadow_root_allocated(kvm); > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 7e66d7c426c1..01808cdf8627 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -4713,8 +4713,7 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) > return direct_page_fault(vcpu, fault); > } > > -static int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, > - u8 *level) > +int kvm_tdp_map_page(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code, u8 *level) > { > int r; > > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > index 37b3769a5d32..019b43723d90 100644 > --- a/arch/x86/kvm/mmu/tdp_mmu.c > +++ b/arch/x86/kvm/mmu/tdp_mmu.c > @@ -1911,16 +1911,13 @@ bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm, > * > * Must be called between kvm_tdp_mmu_walk_lockless_{begin,end}. > */ > -int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, > - int *root_level) > +static int __kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, > + struct kvm_mmu_page *root) > { > - struct kvm_mmu_page *root = root_to_sp(vcpu->arch.mmu->root.hpa); > struct tdp_iter iter; > gfn_t gfn = addr >> PAGE_SHIFT; > int leaf = -1; > > - *root_level = vcpu->arch.mmu->root_role.level; > - > tdp_mmu_for_each_pte(iter, vcpu->kvm, root, gfn, gfn + 1) { > leaf = iter.level; > sptes[leaf] = iter.old_spte; > @@ -1929,6 +1926,36 @@ int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, > return leaf; > } > > +int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, > + int *root_level) > +{ > + struct kvm_mmu_page *root = root_to_sp(vcpu->arch.mmu->root.hpa); > + *root_level = vcpu->arch.mmu->root_role.level; > + > + return __kvm_tdp_mmu_get_walk(vcpu, addr, sptes, root); > +} > + > +bool kvm_tdp_mmu_gpa_is_mapped(struct kvm_vcpu *vcpu, u64 gpa) > +{ > + struct kvm *kvm = vcpu->kvm; > + bool is_direct = kvm_is_addr_direct(kvm, gpa); > + hpa_t root = is_direct ? vcpu->arch.mmu->root.hpa : > + vcpu->arch.mmu->mirror_root_hpa; > + u64 sptes[PT64_ROOT_MAX_LEVEL + 1], spte; > + int leaf; > + > + lockdep_assert_held(&kvm->mmu_lock); > + rcu_read_lock(); > + leaf = __kvm_tdp_mmu_get_walk(vcpu, gpa, sptes, root_to_sp(root)); > + rcu_read_unlock(); > + if (leaf < 0) > + return false; > + > + spte = sptes[leaf]; > + return is_shadow_present_pte(spte) && is_last_spte(spte, leaf); > +} > +EXPORT_SYMBOL_GPL(kvm_tdp_mmu_gpa_is_mapped); > + > /* > * Returns the last level spte pointer of the shadow page walk for the given > * gpa, and sets *spte to the spte value. This spte may be non-preset. If no Reviewed-by: Paolo Bonzini I will take another look at the locking after I see some callers. Paolo