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a=ed25519-sha256; t=1774563861; l=7356; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=rr13v0ReufuLtKHyRyN4FDB898pT6Hlku9bGOsppn1A=; b=nFeFzTX8ygVbPanVDLq7QCIuwm0m3IM+MkQCg+3Y/ZgpL4egW6yC/P2AYDQ3LIc1fpYcY3/Vc q5YdI9LOQx9CHKVyQhNKOkJtQCHUwiYrJZy8/+KcXHHCuWBiotb3HSv X-Mailer: b4 0.14.3 Message-ID: <20260326-gmem-inplace-conversion-v4-8-e202fe950ffd@google.com> Subject: [PATCH RFC v4 08/44] KVM: Introduce KVM_SET_MEMORY_ATTRIBUTES2 From: Ackerley Tng To: aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, ira.weiny@intel.com, jmattson@google.com, jroedel@suse.de, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, tabba@google.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Jason Gunthorpe , Vlastimil Babka Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, 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. Handle KVM_CAP_MEMORY_ATTRIBUTES2 and return the same supported attributes as would be returned for KVM_CAP_MEMORY_ATTRIBUTES - the supported attributes are the same for now, regardless of the CAP requested. 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 | 40 +++++++++++++++++++++++++++++++++++++--- 3 files changed, 81 insertions(+), 3 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 032516783e962..0b61e2579e1d8 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6359,6 +6359,8 @@ 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 ------------------------------- @@ -6551,6 +6553,36 @@ KVM_S390_KEYOP_SSKE Sets the storage key for the guest address ``guest_addr`` to the key specified in ``key``, returning the previous value in ``key``. +4.145 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: 5. The kvm_run structure diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 80364d4dbebb0..16567d4a769e5 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -989,6 +989,7 @@ struct kvm_enable_cap { #define KVM_CAP_ARM_SEA_TO_USER 245 #define KVM_CAP_S390_USER_OPEREXEC 246 #define KVM_CAP_S390_KEYOP 247 +#define KVM_CAP_MEMORY_ATTRIBUTES2 248 struct kvm_irq_routing_irqchip { __u32 irqchip; @@ -1637,6 +1638,17 @@ 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 70b594dafc5cc..3c261904322f0 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2621,9 +2621,10 @@ 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; + int i; /* flags is currently not used. */ if (attrs->flags) @@ -2634,6 +2635,10 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm, return -EINVAL; if (!PAGE_ALIGNED(attrs->address) || !PAGE_ALIGNED(attrs->size)) return -EINVAL; + for (i = 0; i < ARRAY_SIZE(attrs->reserved); i++) { + if (attrs->reserved[i]) + return -EINVAL; + } start = attrs->address >> PAGE_SHIFT; end = (attrs->address + attrs->size) >> PAGE_SHIFT; @@ -4966,6 +4971,7 @@ 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; @@ -5191,6 +5197,14 @@ 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) { @@ -5373,15 +5387,35 @@ 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); -- 2.53.0.1018.g2bb0e51243-goog