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[34.105.13.176]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22c33fa7638sm15905665ad.142.2025.04.16.08.53.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Apr 2025 08:53:54 -0700 (PDT) Date: Wed, 16 Apr 2025 08:53:49 -0700 From: Vipin Sharma To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/3] KVM: x86/mmu: Dynamically allocate shadow MMU's hashed page list Message-ID: <20250416155349.GA701848.vipinsh@google.com> References: <20250401155714.838398-1-seanjc@google.com> <20250401155714.838398-2-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250401155714.838398-2-seanjc@google.com> On 2025-04-01 08:57:12, Sean Christopherson wrote: > Dynamically allocate the (massive) array of hashed lists used to track > shadow pages, as the array itself is 32KiB, i.e. is an order-3 allocation > all on its own, and is *exactly* an order-3 allocation. Dynamically > allocating the array will allow allocating "struct kvm" using regular > kmalloc(), and will also allow deferring allocation of the array until > it's actually needed, i.e. until the first shadow root is allocated. > > Cc: Vipin Sharma > Signed-off-by: Sean Christopherson > --- > arch/x86/include/asm/kvm_host.h | 4 ++-- > arch/x86/kvm/mmu/mmu.c | 23 ++++++++++++++++++++++- > arch/x86/kvm/x86.c | 5 ++++- > 3 files changed, 28 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index a884ab544335..e523d7d8a107 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1333,7 +1333,7 @@ struct kvm_arch { > bool has_private_mem; > bool has_protected_state; > bool pre_fault_allowed; > - struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES]; > + struct hlist_head *mmu_page_hash; > struct list_head active_mmu_pages; > /* > * A list of kvm_mmu_page structs that, if zapped, could possibly be > @@ -1985,7 +1985,7 @@ void kvm_mmu_vendor_module_exit(void); > > void kvm_mmu_destroy(struct kvm_vcpu *vcpu); > int kvm_mmu_create(struct kvm_vcpu *vcpu); > -void kvm_mmu_init_vm(struct kvm *kvm); > +int kvm_mmu_init_vm(struct kvm *kvm); > void kvm_mmu_uninit_vm(struct kvm *kvm); > > void kvm_mmu_init_memslot_memory_attributes(struct kvm *kvm, > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 63bb77ee1bb1..6b9c72405860 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -3880,6 +3880,18 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) > return r; > } > > +static int kvm_mmu_alloc_page_hash(struct kvm *kvm) > +{ > + typeof(kvm->arch.mmu_page_hash) h; > + > + h = kcalloc(KVM_NUM_MMU_PAGES, sizeof(*h), GFP_KERNEL_ACCOUNT); > + if (!h) > + return -ENOMEM; > + > + kvm->arch.mmu_page_hash = h; > + return 0; > +} > + > static int mmu_first_shadow_root_alloc(struct kvm *kvm) > { > struct kvm_memslots *slots; > @@ -6673,13 +6685,19 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm) > kvm_tdp_mmu_zap_invalidated_roots(kvm, true); > } > > -void kvm_mmu_init_vm(struct kvm *kvm) > +int kvm_mmu_init_vm(struct kvm *kvm) > { > + int r; > + > kvm->arch.shadow_mmio_value = shadow_mmio_value; > INIT_LIST_HEAD(&kvm->arch.active_mmu_pages); > INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages); > spin_lock_init(&kvm->arch.mmu_unsync_pages_lock); > > + r = kvm_mmu_alloc_page_hash(kvm); > + if (r) > + return r; > + > if (tdp_mmu_enabled) > kvm_mmu_init_tdp_mmu(kvm); > > @@ -6690,6 +6708,7 @@ void kvm_mmu_init_vm(struct kvm *kvm) > > kvm->arch.split_desc_cache.kmem_cache = pte_list_desc_cache; > kvm->arch.split_desc_cache.gfp_zero = __GFP_ZERO; > + return 0; > } > > static void mmu_free_vm_memory_caches(struct kvm *kvm) > @@ -6701,6 +6720,8 @@ static void mmu_free_vm_memory_caches(struct kvm *kvm) > > void kvm_mmu_uninit_vm(struct kvm *kvm) > { > + kfree(kvm->arch.mmu_page_hash); > + > if (tdp_mmu_enabled) > kvm_mmu_uninit_tdp_mmu(kvm); > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index c841817a914a..4070f9d34521 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -12721,7 +12721,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) > if (ret) > goto out; > > - kvm_mmu_init_vm(kvm); > + ret = kvm_mmu_init_vm(kvm); > + if (ret) > + goto out_cleanup_page_track; > > ret = kvm_x86_call(vm_init)(kvm); > if (ret) > @@ -12774,6 +12776,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) > > out_uninit_mmu: > kvm_mmu_uninit_vm(kvm); > +out_cleanup_page_track: > kvm_page_track_cleanup(kvm); > out: > return ret; > -- > 2.49.0.472.ge94155a9ec-goog > Reviewed-by: Vipin Sharma