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AJvYcCXn3i4ZTpV2Os7MQVwRfUuZCa6hCx8UUU2opU6hQKlmExLQCRbq+bF4z3UBZVCH+IDjbM0mAEY=@lists.linux.dev X-Gm-Message-State: AOJu0Yzry5wEIvczIAGmlj7tqc9bTq5dDYtUJPjyPtkkxZi/f8bMSmLp 8VZ5dGAwRQAWdp0DhEjAipMDTTwL2RAwrQNqZpxxX17acFkifB0OYBQV8sVtRVAY64vytevZnWx XGQ== X-Google-Smtp-Source: AGHT+IEM/pEma3Sd9qaIbeLMaRF9FjzoCSs8lhQkRdTlI2IxORmEAPPSn935X/OEjBNHP0I9VmmcSxrzDA== X-Received: from wmbhe12.prod.google.com ([2002:a05:600c:540c:b0:450:d104:29f8]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:24c8:b0:3b5:e31e:5bb6 with SMTP id ffacd0b85a97d-3b5e458893emr1540506f8f.42.1752058822807; Wed, 09 Jul 2025 04:00:22 -0700 (PDT) Date: Wed, 9 Jul 2025 11:59:42 +0100 In-Reply-To: <20250709105946.4009897-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250709105946.4009897-1-tabba@google.com> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250709105946.4009897-17-tabba@google.com> Subject: [PATCH v13 16/20] 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, kvmarm@lists.linux.dev 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 architecture support for handling guest page faults on memory slots backed by guest_memfd. This change introduces a new function, gmem_abort(), which encapsulates the fault handling logic specific to guest_memfd-backed memory. The kvm_handle_guest_abort() entry point is updated to dispatch to gmem_abort() when a fault occurs on a guest_memfd-backed memory slot (as determined by kvm_slot_has_gmem()). Until guest_memfd gains support for huge pages, the fault granule for these memory regions is restricted to PAGE_SIZE. Reviewed-by: Gavin Shan Reviewed-by: James Houghton Signed-off-by: Fuad Tabba --- arch/arm64/kvm/mmu.c | 82 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 79 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 58662e0ef13e..71f8b53683e7 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1512,6 +1512,78 @@ static void adjust_nested_fault_perms(struct kvm_s2_trans *nested, *prot |= kvm_encode_nested_level(nested); } +#define KVM_PGTABLE_WALK_MEMABORT_FLAGS (KVM_PGTABLE_WALK_HANDLE_FAULT | KVM_PGTABLE_WALK_SHARED) + +static int gmem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, + struct kvm_s2_trans *nested, + struct kvm_memory_slot *memslot, bool is_perm) +{ + bool write_fault, exec_fault, writable; + enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_MEMABORT_FLAGS; + enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R; + struct kvm_pgtable *pgt = vcpu->arch.hw_mmu->pgt; + struct page *page; + struct kvm *kvm = vcpu->kvm; + void *memcache; + kvm_pfn_t pfn; + gfn_t gfn; + int ret; + + ret = prepare_mmu_memcache(vcpu, true, &memcache); + if (ret) + return ret; + + if (nested) + gfn = kvm_s2_trans_output(nested) >> PAGE_SHIFT; + else + gfn = fault_ipa >> PAGE_SHIFT; + + write_fault = kvm_is_write_fault(vcpu); + exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu); + + if (write_fault && exec_fault) { + kvm_err("Simultaneous write and execution fault\n"); + return -EFAULT; + } + + if (is_perm && !write_fault && !exec_fault) { + kvm_err("Unexpected L2 read permission error\n"); + return -EFAULT; + } + + ret = kvm_gmem_get_pfn(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); + + if (nested) + adjust_nested_fault_perms(nested, &prot, &writable); + + if (writable) + prot |= KVM_PGTABLE_PROT_W; + + if (exec_fault || + (cpus_have_final_cap(ARM64_HAS_CACHE_DIC) && + (!nested || kvm_s2_trans_executable(nested)))) + prot |= KVM_PGTABLE_PROT_X; + + kvm_fault_lock(kvm); + 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, @@ -1536,7 +1608,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R; struct kvm_pgtable *pgt; struct page *page; - enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_HANDLE_FAULT | KVM_PGTABLE_WALK_SHARED; + enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_MEMABORT_FLAGS; if (fault_is_perm) fault_granule = kvm_vcpu_trap_get_perm_fault_granule(vcpu); @@ -1963,8 +2035,12 @@ 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, nested, 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: -- 2.50.0.727.gbf7dc18ff4-goog