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AJvYcCWg9aMvQ8QlIftYcviMtAqHH2Z4Y0fBsANTOX0DNN783eRNyi8vecH8xls31F6rY5w2uHo2j4ScCHzSW211@vger.kernel.org X-Gm-Message-State: AOJu0Yx+WTzQUMWdE45VeZY3cScVryBtiC6FJR9LVJvmKGBTawYFdNbO yBc43KRhEH8QlP3KFJs7JdQrfINJ8UYrUDNril9ZstxqpvLcId4lmqw4U3qbZcz9gv92Y6I5MQ= = X-Google-Smtp-Source: AGHT+IEjjYEXEYlvWFF5OLq9cklfBFuKA7pxlcIDeCLfcHXQdKGj5SSIieh7nJvEEf5f7+rXBSzijM2YeA== X-Received: from wmsd3.prod.google.com ([2002:a05:600c:3ac3:b0:442:dc9b:b569]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:5118:b0:43d:cc9:b09d with SMTP id 5b1f17b1804b1-442d6dc539cmr116558185e9.20.1747154106776; Tue, 13 May 2025 09:35:06 -0700 (PDT) Date: Tue, 13 May 2025 17:34:34 +0100 In-Reply-To: <20250513163438.3942405-1-tabba@google.com> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250513163438.3942405-1-tabba@google.com> X-Mailer: git-send-email 2.49.0.1045.g170613ef41-goog Message-ID: <20250513163438.3942405-14-tabba@google.com> Subject: [PATCH v9 13/17] KVM: arm64: Handle guest_memfd()-backed guest page faults From: Fuad Tabba To: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com, tabba@google.com Add arm64 support for handling guest page faults on guest_memfd backed memslots. For now, the fault granule is restricted to PAGE_SIZE. Signed-off-by: Fuad Tabba --- arch/arm64/kvm/mmu.c | 94 +++++++++++++++++++++++++--------------- include/linux/kvm_host.h | 5 +++ virt/kvm/kvm_main.c | 5 --- 3 files changed, 64 insertions(+), 40 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index d756c2b5913f..9a48ef08491d 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1466,6 +1466,30 @@ static bool kvm_vma_mte_allowed(struct vm_area_struct *vma) return vma->vm_flags & VM_MTE_ALLOWED; } +static kvm_pfn_t faultin_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, bool write_fault, bool *writable, + struct page **page, bool is_gmem) +{ + kvm_pfn_t pfn; + int ret; + + if (!is_gmem) + return __kvm_faultin_pfn(slot, gfn, write_fault ? FOLL_WRITE : 0, writable, page); + + *writable = false; + + ret = kvm_gmem_get_pfn(kvm, slot, gfn, &pfn, page, NULL); + if (!ret) { + *writable = !memslot_is_readonly(slot); + return pfn; + } + + if (ret == -EHWPOISON) + return KVM_PFN_ERR_HWPOISON; + + return KVM_PFN_ERR_NOSLOT_MASK; +} + static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, struct kvm_s2_trans *nested, struct kvm_memory_slot *memslot, unsigned long hva, @@ -1473,19 +1497,20 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, { int ret = 0; bool write_fault, writable; - bool exec_fault, mte_allowed; + bool exec_fault, mte_allowed = false; bool device = false, vfio_allow_any_uc = false; unsigned long mmu_seq; phys_addr_t ipa = fault_ipa; struct kvm *kvm = vcpu->kvm; - struct vm_area_struct *vma; - short page_shift; + struct vm_area_struct *vma = NULL; + short page_shift = PAGE_SHIFT; void *memcache; - gfn_t gfn; + gfn_t gfn = ipa >> PAGE_SHIFT; kvm_pfn_t pfn; bool logging_active = memslot_is_logging(memslot); - bool force_pte = logging_active || is_protected_kvm_enabled(); - long page_size, fault_granule; + bool is_gmem = kvm_slot_has_gmem(memslot); + bool force_pte = logging_active || is_gmem || is_protected_kvm_enabled(); + long page_size, fault_granule = PAGE_SIZE; enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R; struct kvm_pgtable *pgt; struct page *page; @@ -1529,17 +1554,20 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, * Let's check if we will get back a huge page backed by hugetlbfs, or * get block mapping for device MMIO region. */ - mmap_read_lock(current->mm); - vma = vma_lookup(current->mm, hva); - if (unlikely(!vma)) { - kvm_err("Failed to find VMA for hva 0x%lx\n", hva); - mmap_read_unlock(current->mm); - return -EFAULT; + if (!is_gmem) { + mmap_read_lock(current->mm); + vma = vma_lookup(current->mm, hva); + if (unlikely(!vma)) { + kvm_err("Failed to find VMA for hva 0x%lx\n", hva); + mmap_read_unlock(current->mm); + return -EFAULT; + } + + vfio_allow_any_uc = vma->vm_flags & VM_ALLOW_ANY_UNCACHED; + mte_allowed = kvm_vma_mte_allowed(vma); } - if (force_pte) - page_shift = PAGE_SHIFT; - else + if (!force_pte) page_shift = get_vma_page_shift(vma, hva); switch (page_shift) { @@ -1605,27 +1633,23 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, ipa &= ~(page_size - 1); } - gfn = ipa >> PAGE_SHIFT; - mte_allowed = kvm_vma_mte_allowed(vma); - - vfio_allow_any_uc = vma->vm_flags & VM_ALLOW_ANY_UNCACHED; - - /* Don't use the VMA after the unlock -- it may have vanished */ - vma = NULL; + if (!is_gmem) { + /* Don't use the VMA after the unlock -- it may have vanished */ + vma = NULL; - /* - * Read mmu_invalidate_seq so that KVM can detect if the results of - * vma_lookup() or __kvm_faultin_pfn() become stale prior to - * acquiring kvm->mmu_lock. - * - * Rely on mmap_read_unlock() for an implicit smp_rmb(), which pairs - * with the smp_wmb() in kvm_mmu_invalidate_end(). - */ - mmu_seq = vcpu->kvm->mmu_invalidate_seq; - mmap_read_unlock(current->mm); + /* + * Read mmu_invalidate_seq so that KVM can detect if the results + * of vma_lookup() or faultin_pfn() become stale prior to + * acquiring kvm->mmu_lock. + * + * Rely on mmap_read_unlock() for an implicit smp_rmb(), which + * pairs with the smp_wmb() in kvm_mmu_invalidate_end(). + */ + mmu_seq = vcpu->kvm->mmu_invalidate_seq; + mmap_read_unlock(current->mm); + } - pfn = __kvm_faultin_pfn(memslot, gfn, write_fault ? FOLL_WRITE : 0, - &writable, &page); + pfn = faultin_pfn(kvm, memslot, gfn, write_fault, &writable, &page, is_gmem); if (pfn == KVM_PFN_ERR_HWPOISON) { kvm_send_hwpoison_signal(hva, page_shift); return 0; @@ -1677,7 +1701,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, kvm_fault_lock(kvm); pgt = vcpu->arch.hw_mmu->pgt; - if (mmu_invalidate_retry(kvm, mmu_seq)) { + if (!is_gmem && mmu_invalidate_retry(kvm, mmu_seq)) { ret = -EAGAIN; goto out_unlock; } diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index f9bb025327c3..b317392453a5 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1884,6 +1884,11 @@ static inline int memslot_id(struct kvm *kvm, gfn_t gfn) return gfn_to_memslot(kvm, gfn)->id; } +static inline bool memslot_is_readonly(const struct kvm_memory_slot *slot) +{ + return slot->flags & KVM_MEM_READONLY; +} + static inline gfn_t hva_to_gfn_memslot(unsigned long hva, struct kvm_memory_slot *slot) { diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 6289ea1685dd..6261d8638cd2 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2640,11 +2640,6 @@ unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn) return size; } -static bool memslot_is_readonly(const struct kvm_memory_slot *slot) -{ - return slot->flags & KVM_MEM_READONLY; -} - static unsigned long __gfn_to_hva_many(const struct kvm_memory_slot *slot, gfn_t gfn, gfn_t *nr_pages, bool write) {