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AJvYcCWf23VJIGkBnn8koRW+uMiZicLE5mbFRzsHQGWwIk8v9nSF9TgA+nMcavImT+melpITD3B/1MQfccx9yEKTda86C/w=@vger.kernel.org X-Gm-Message-State: AOJu0YwIPvMHKzxPdKhD+S2/G0U2B3m8uD8C0+2P7mMbtrLk6Py7JdmS AcZFSbsBWKRSVBSlu30pe1pPCCFl7COJI9a5h1U+0YuQHhDNs400qJvcvn2wxGJOqvzEcSMPrUR L+hVA/X8lRonkUJe/w5h8++IHrQ== X-Received: from plqu1.prod.google.com ([2002:a17:902:a601:b0:2a0:86e1:5be6]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:ebd2:b0:29f:f91:35ee with SMTP id d9443c01a7336-2a8d9a5f1bcmr132785965ad.43.1770071434221; Mon, 02 Feb 2026 14:30:34 -0800 (PST) Date: Mon, 2 Feb 2026 14:29:45 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: X-Mailer: git-send-email 2.53.0.rc1.225.gd81095ad13-goog Message-ID: <2b16d30fc0606046574e4df0e0a93afdd4bad836.1770071243.git.ackerleytng@google.com> Subject: [RFC PATCH v2 07/37] KVM: Introduce KVM_SET_MEMORY_ATTRIBUTES2 From: Ackerley Tng To: kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org Cc: aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, bp@alien8.de, brauner@kernel.org, chao.p.peng@intel.com, chao.p.peng@linux.intel.com, chenhuacai@kernel.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, hpa@zytor.com, ira.weiny@intel.com, jgg@nvidia.com, jmattson@google.com, jroedel@suse.de, jthoughton@google.com, maobibo@loongson.cn, mathieu.desnoyers@efficios.com, maz@kernel.org, mhiramat@kernel.org, michael.roth@amd.com, mingo@redhat.com, mlevitsk@redhat.com, oupton@kernel.org, pankaj.gupta@amd.com, pbonzini@redhat.com, prsampat@amd.com, qperret@google.com, ricarkol@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, rostedt@goodmis.org, seanjc@google.com, shivankg@amd.com, shuah@kernel.org, steven.price@arm.com, tabba@google.com, tglx@linutronix.de, vannapurve@google.com, vbabka@suse.cz, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, Ackerley Tng Content-Type: text/plain; charset="UTF-8" Introduce a "version 2" of KVM_SET_MEMORY_ATTRIBUTES to support returning information back to userspace. This new ioctl and structure will, in a later patch, be shared as a guest_memfd ioctl, where the padding in the new kvm_memory_attributes2 structure will be for writing the response from the guest_memfd ioctl to userspace. A new ioctl is necessary for these reasons: 1. KVM_SET_MEMORY_ATTRIBUTES is currently a write-only ioctl and does not allow userspace to read fields. There's nothing in code (yet?) that validates this, but using _IOWR for consistency would be prudent. 2. KVM_SET_MEMORY_ATTRIBUTES, when used as a guest_memfd ioctl, will need an additional field to provide userspace with more error details. Alternatively, a completely new ioctl could be defined, unrelated to KVM_SET_MEMORY_ATTRIBUTES, but using the same ioctl number and struct for the vm and guest_memfd ioctls streamlines the interface for userspace. In addition, any memory attributes, implemented on the vm or guest_memfd ioctl, can be easily shared with the other. Add KVM_CAP_MEMORY_ATTRIBUTES2 to indicate that struct kvm_memory_attributes2 exists and can be used either with KVM_SET_MEMORY_ATTRIBUTES2 via the vm or guest_memfd ioctl. Since KVM_SET_MEMORY_ATTRIBUTES2 is not limited to be used only with the vm ioctl, return 1 for KVM_CAP_MEMORY_ATTRIBUTES2 as long as struct kvm_memory_attributes2 and KVM_SET_MEMORY_ATTRIBUTES2 can be used. KVM_CAP_MEMORY_ATTRIBUTES must still be used to actually get valid attributes. Handle KVM_CAP_MEMORY_ATTRIBUTES2 and return 1 regardless of CONFIG_KVM_VM_MEMORY_ATTRIBUTES, since KVM_SET_MEMORY_ATTRIBUTES2 is not limited to a vm ioctl and can also be used with the guest_memfd ioctl. Suggested-by: Sean Christopherson Signed-off-by: Ackerley Tng --- Documentation/virt/kvm/api.rst | 32 +++++++++++++++++++++++++++++++ include/uapi/linux/kvm.h | 12 ++++++++++++ virt/kvm/kvm_main.c | 35 +++++++++++++++++++++++++++++++--- 3 files changed, 76 insertions(+), 3 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 01a3abef8abb..23ec0b0c3e22 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6360,6 +6360,8 @@ S390: Returns -EINVAL if the VM has the KVM_VM_S390_UCONTROL flag set. Returns -EINVAL if called on a protected VM. +.. _KVM_SET_MEMORY_ATTRIBUTES: + 4.141 KVM_SET_MEMORY_ATTRIBUTES ------------------------------- @@ -6517,6 +6519,36 @@ the capability to be present. `flags` must currently be zero. +4.144 KVM_SET_MEMORY_ATTRIBUTES2 +--------------------------------- + +:Capability: KVM_CAP_MEMORY_ATTRIBUTES2 +:Architectures: x86 +:Type: vm ioctl +:Parameters: struct kvm_memory_attributes2 (in/out) +:Returns: 0 on success, <0 on error + +KVM_SET_MEMORY_ATTRIBUTES2 is an extension to +KVM_SET_MEMORY_ATTRIBUTES that supports returning (writing) values to +userspace. The original (pre-extension) fields are shared with +KVM_SET_MEMORY_ATTRIBUTES identically. + +Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES. + +:: + + struct kvm_memory_attributes2 { + __u64 address; + __u64 size; + __u64 attributes; + __u64 flags; + __u64 reserved[12]; + }; + + #define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3) + +See also: :ref: `KVM_SET_MEMORY_ATTRIBUTES`. + .. _kvm_run: diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index dddb781b0507..7f8dac4f4fd3 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -974,6 +974,7 @@ struct kvm_enable_cap { #define KVM_CAP_GUEST_MEMFD_FLAGS 244 #define KVM_CAP_ARM_SEA_TO_USER 245 #define KVM_CAP_S390_USER_OPEREXEC 246 +#define KVM_CAP_MEMORY_ATTRIBUTES2 247 struct kvm_irq_routing_irqchip { __u32 irqchip; @@ -1607,6 +1608,17 @@ struct kvm_memory_attributes { __u64 flags; }; +/* Available with KVM_CAP_MEMORY_ATTRIBUTES2 */ +#define KVM_SET_MEMORY_ATTRIBUTES2 _IOWR(KVMIO, 0xd2, struct kvm_memory_attributes2) + +struct kvm_memory_attributes2 { + __u64 address; + __u64 size; + __u64 attributes; + __u64 flags; + __u64 reserved[12]; +}; + #define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3) #define KVM_CREATE_GUEST_MEMFD _IOWR(KVMIO, 0xd4, struct kvm_create_guest_memfd) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 666d1f7fbf07..ad70101c2e3f 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2637,7 +2637,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end, return r; } static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm, - struct kvm_memory_attributes *attrs) + struct kvm_memory_attributes2 *attrs) { gfn_t start, end; @@ -4981,6 +4981,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) case KVM_CAP_DEVICE_CTRL: return 1; #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES + case KVM_CAP_MEMORY_ATTRIBUTES2: case KVM_CAP_MEMORY_ATTRIBUTES: if (!vm_memory_attributes) return 0; @@ -5206,6 +5207,14 @@ do { \ sizeof_field(struct kvm_userspace_memory_region2, field)); \ } while (0) +#define SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(field) \ +do { \ + BUILD_BUG_ON(offsetof(struct kvm_memory_attributes, field) != \ + offsetof(struct kvm_memory_attributes2, field)); \ + BUILD_BUG_ON(sizeof_field(struct kvm_memory_attributes, field) != \ + sizeof_field(struct kvm_memory_attributes2, field)); \ +} while (0) + static long kvm_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) { @@ -5388,15 +5397,35 @@ static long kvm_vm_ioctl(struct file *filp, } #endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */ #ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES + case KVM_SET_MEMORY_ATTRIBUTES2: case KVM_SET_MEMORY_ATTRIBUTES: { - struct kvm_memory_attributes attrs; + struct kvm_memory_attributes2 attrs; + unsigned long size; + + if (ioctl == KVM_SET_MEMORY_ATTRIBUTES) { + /* + * Fields beyond struct kvm_memory_attributes shouldn't + * be accessed, but avoid leaking kernel memory in case + * of a bug. + */ + memset(&attrs, 0, sizeof(attrs)); + size = sizeof(struct kvm_memory_attributes); + } else { + size = sizeof(struct kvm_memory_attributes2); + } + + /* Ensure the common parts of the two structs are identical. */ + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(address); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(size); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(attributes); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(flags); r = -ENOTTY; if (!vm_memory_attributes) goto out; r = -EFAULT; - if (copy_from_user(&attrs, argp, sizeof(attrs))) + if (copy_from_user(&attrs, argp, size)) goto out; r = kvm_vm_ioctl_set_mem_attributes(kvm, &attrs); -- 2.53.0.rc1.225.gd81095ad13-goog