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AJvYcCWnXH80tJKx+GZQwIQphJX6EOi1b67rT82HOQ7FyTN7mHX85kXJP93WVJHqcJo+IUWw8OazUlxsUXsSi2wr@vger.kernel.org X-Gm-Message-State: AOJu0Yx5DkzWubExMF1slf0UfW/qSDPk54t2AyUIPCWBmoZJ9OIC2239 jXYXqoXWo0MYmOq4WstH2a3K7vMBBSsiDRePKIyS5rX/HZ+UgP+CQLGFnwfP1L86V7/sg0uSg1V Cpw== X-Google-Smtp-Source: AGHT+IHCf0bDJ76hTT4kSC4YiVQWOuaVECuOWgSL6WNt6PYLNGGO9OXNopWm7SAaIEhfPW/80Tr8Ykb3uA== X-Received: from wmbed10.prod.google.com ([2002:a05:600c:614a:b0:442:ccfa:102]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:512a:b0:44b:2f53:351c with SMTP id 5b1f17b1804b1-44c91dcb6e7mr133582365e9.18.1748368993658; Tue, 27 May 2025 11:03:13 -0700 (PDT) Date: Tue, 27 May 2025 19:02:42 +0100 In-Reply-To: <20250527180245.1413463-1-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: <20250527180245.1413463-1-tabba@google.com> X-Mailer: git-send-email 2.49.0.1164.gab81da1b16-goog Message-ID: <20250527180245.1413463-14-tabba@google.com> Subject: [PATCH v10 13/16] 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 Content-Type: text/plain; charset="UTF-8" Add arm64 support for handling guest page faults on guest_memfd backed memslots. Until guest_memfd supports huge pages, the fault granule is restricted to PAGE_SIZE. Signed-off-by: Fuad Tabba --- Note: This patch introduces a new function, gmem_abort() rather than previous attempts at trying to expand user_mem_abort(). This is because there are many differences in how faults are handled when backed by guest_memfd vs regular memslots with anonymous memory, e.g., lack of VMA, and for now, lack of huge page support for guest_memfd. The function user_mem_abort() is already big and unwieldly, adding more complexity to it made things more difficult to understand. Once larger page size support is added to guest_memfd, we could factor out the common code between these two functions. --- arch/arm64/kvm/mmu.c | 89 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 87 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 9865ada04a81..896c56683d88 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1466,6 +1466,87 @@ static bool kvm_vma_mte_allowed(struct vm_area_struct *vma) return vma->vm_flags & VM_MTE_ALLOWED; } +static int gmem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, + struct kvm_memory_slot *memslot, bool is_perm) +{ + enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_HANDLE_FAULT | KVM_PGTABLE_WALK_SHARED; + enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R; + bool logging, write_fault, exec_fault, writable; + struct kvm_pgtable *pgt; + struct page *page; + struct kvm *kvm; + void *memcache; + kvm_pfn_t pfn; + gfn_t gfn; + int ret; + + if (!is_perm) { + int min_pages = kvm_mmu_cache_min_pages(vcpu->arch.hw_mmu); + + if (!is_protected_kvm_enabled()) { + memcache = &vcpu->arch.mmu_page_cache; + ret = kvm_mmu_topup_memory_cache(memcache, min_pages); + } else { + memcache = &vcpu->arch.pkvm_memcache; + ret = topup_hyp_memcache(memcache, min_pages); + } + if (ret) + return ret; + } + + kvm = vcpu->kvm; + gfn = fault_ipa >> PAGE_SHIFT; + + logging = memslot_is_logging(memslot); + write_fault = kvm_is_write_fault(vcpu); + exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu); + VM_BUG_ON(write_fault && exec_fault); + + if (is_perm && !write_fault && !exec_fault) { + kvm_err("Unexpected L2 read permission error\n"); + return -EFAULT; + } + + ret = kvm_gmem_get_pfn(vcpu->kvm, memslot, gfn, &pfn, &page, NULL); + if (ret) { + kvm_prepare_memory_fault_exit(vcpu, fault_ipa, PAGE_SIZE, + write_fault, exec_fault, false); + return ret; + } + + writable = !(memslot->flags & KVM_MEM_READONLY) && + (!logging || write_fault); + + if (writable) + prot |= KVM_PGTABLE_PROT_W; + + if (exec_fault || cpus_have_final_cap(ARM64_HAS_CACHE_DIC)) + prot |= KVM_PGTABLE_PROT_X; + + pgt = vcpu->arch.hw_mmu->pgt; + + kvm_fault_lock(kvm); + if (is_perm) { + /* + * Drop the SW bits in favour of those stored in the + * PTE, which will be preserved. + */ + prot &= ~KVM_NV_GUEST_MAP_SZ; + ret = KVM_PGT_FN(kvm_pgtable_stage2_relax_perms)(pgt, fault_ipa, prot, flags); + } else { + ret = KVM_PGT_FN(kvm_pgtable_stage2_map)(pgt, fault_ipa, PAGE_SIZE, + __pfn_to_phys(pfn), prot, + memcache, flags); + } + kvm_release_faultin_page(kvm, page, !!ret, writable); + kvm_fault_unlock(kvm); + + if (writable && !ret) + mark_page_dirty_in_slot(kvm, memslot, gfn); + + return ret != -EAGAIN ? ret : 0; +} + 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, @@ -1944,8 +2025,12 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) goto out_unlock; } - ret = user_mem_abort(vcpu, fault_ipa, nested, memslot, hva, - esr_fsc_is_permission_fault(esr)); + if (kvm_slot_has_gmem(memslot)) + ret = gmem_abort(vcpu, fault_ipa, memslot, + esr_fsc_is_permission_fault(esr)); + else + ret = user_mem_abort(vcpu, fault_ipa, nested, memslot, hva, + esr_fsc_is_permission_fault(esr)); if (ret == 0) ret = 1; out: -- 2.49.0.1164.gab81da1b16-goog