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AJvYcCUbKI43S+uA/i0Z2lAA6H+p7UT+35hFXoCN8CKwgPriPiZgl8fUtXPl8Iyo7mrB6AYq85SKM/XndA==@kvack.org X-Gm-Message-State: AOJu0Yz52lRr8933jhPDxG6pTSJ5FbF4nUyJ5TcR1wJN3sbp8s9q3/IS T9DXG6BsJMjVGeN02RFDrkVkshZYEHXbYovys0vf5LNuH67xVl0yi3vAFwuZ8nlku2p0XrxrxKy rpg== X-Google-Smtp-Source: AGHT+IHX8EI5JXc2m1Ub6jRFvHKhxx/iMkDQpy+4Lc0WVLTknDLg7nWPPGgOQGFU7U2VLXzeD+QYo91L5w== X-Received: from wmth13.prod.google.com ([2002:a05:600c:8b6d:b0:450:dc81:eec9]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:2006:b0:3b4:990b:9ee7 with SMTP id ffacd0b85a97d-3b5e453117emr1323755f8f.22.1752058826920; Wed, 09 Jul 2025 04:00:26 -0700 (PDT) Date: Wed, 9 Jul 2025 11:59:44 +0100 In-Reply-To: <20250709105946.4009897-1-tabba@google.com> Mime-Version: 1.0 References: <20250709105946.4009897-1-tabba@google.com> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250709105946.4009897-19-tabba@google.com> Subject: [PATCH v13 18/20] KVM: Introduce the KVM capability KVM_CAP_GMEM_MMAP 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" X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 9881510001C X-Stat-Signature: k6p4qeckgcg397red3rwfx4ddqsbmxx7 X-Rspam-User: X-HE-Tag: 1752058828-769731 X-HE-Meta: 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 hkj0RFDR 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Introduce the new KVM capability KVM_CAP_GMEM_MMAP. This capability signals to userspace that a KVM instance supports host userspace mapping of guest_memfd-backed memory. The availability of this capability is determined per architecture, and its enablement for a specific guest_memfd instance is controlled by the GUEST_MEMFD_FLAG_MMAP flag at creation time. Update the KVM API documentation to detail the KVM_CAP_GMEM_MMAP capability, the associated GUEST_MEMFD_FLAG_MMAP, and provide essential information regarding support for mmap in guest_memfd. Reviewed-by: David Hildenbrand Reviewed-by: Gavin Shan Signed-off-by: Fuad Tabba --- Documentation/virt/kvm/api.rst | 9 +++++++++ include/uapi/linux/kvm.h | 1 + virt/kvm/kvm_main.c | 4 ++++ 3 files changed, 14 insertions(+) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 9abf93ee5f65..70261e189162 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6407,6 +6407,15 @@ most one mapping per page, i.e. binding multiple memory regions to a single guest_memfd range is not allowed (any number of memory regions can be bound to a single guest_memfd file, but the bound ranges must not overlap). +When the capability KVM_CAP_GMEM_MMAP is supported, the 'flags' field supports +GUEST_MEMFD_FLAG_MMAP. Setting this flag on guest_memfd creation enables mmap() +and faulting of guest_memfd memory to host userspace. + +When the KVM MMU performs a PFN lookup to service a guest fault and the backing +guest_memfd has the GUEST_MEMFD_FLAG_MMAP set, then the fault will always be +consumed from guest_memfd, regardless of whether it is a shared or a private +fault. + See KVM_SET_USER_MEMORY_REGION2 for additional details. 4.143 KVM_PRE_FAULT_MEMORY diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index c71348db818f..cbf28237af79 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -956,6 +956,7 @@ struct kvm_enable_cap { #define KVM_CAP_ARM_EL2 240 #define KVM_CAP_ARM_EL2_E2H0 241 #define KVM_CAP_RISCV_MP_STATE_RESET 242 +#define KVM_CAP_GMEM_MMAP 243 struct kvm_irq_routing_irqchip { __u32 irqchip; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 81bb18fa8655..5463e81b08b9 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4913,6 +4913,10 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) #ifdef CONFIG_KVM_GMEM case KVM_CAP_GUEST_MEMFD: return !kvm || kvm_arch_supports_gmem(kvm); +#endif +#ifdef CONFIG_KVM_GMEM_SUPPORTS_MMAP + case KVM_CAP_GMEM_MMAP: + return !kvm || kvm_arch_supports_gmem_mmap(kvm); #endif default: break; -- 2.50.0.727.gbf7dc18ff4-goog