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.
Suggested-by: Sean Christopherson seanjc@google.com Signed-off-by: Ackerley Tng ackerleytng@google.com --- 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 754b662a453c3..a812769d79bf6 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6355,6 +6355,8 @@ 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 -------------------------------
@@ -6512,6 +6514,36 @@ 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[4]; + }; + + #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 52f6000ab0208..c300e38c7c9cd 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -963,6 +963,7 @@ struct kvm_enable_cap { #define KVM_CAP_RISCV_MP_STATE_RESET 242 #define KVM_CAP_ARM_CACHEABLE_PFNMAP_SUPPORTED 243 #define KVM_CAP_GUEST_MEMFD_FLAGS 244 +#define KVM_CAP_MEMORY_ATTRIBUTES2 245
struct kvm_irq_routing_irqchip { __u32 irqchip; @@ -1617,4 +1618,15 @@ struct kvm_pre_fault_memory { __u64 padding[5]; };
+/* Available with KVM_CAP_MEMORY_ATTRIBUTES2 */ +#define KVM_SET_MEMORY_ATTRIBUTES2 _IOWR(KVMIO, 0xd6, struct kvm_memory_attributes2) + +struct kvm_memory_attributes2 { + __u64 address; + __u64 size; + __u64 attributes; + __u64 flags; + __u64 reserved[4]; +}; + #endif /* __LINUX_KVM_H */ diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 35166754a22b4..dd84b377e46db 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2621,7 +2621,7 @@ 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;
@@ -4959,6 +4959,7 @@ 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; @@ -5184,6 +5185,14 @@ 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_set_memory_attributes, field) != \ + offsetof(struct kvm_set_memory_attributes2, field)); \ + BUILD_BUG_ON(sizeof_field(struct kvm_set_memory_attributes, field) != \ + sizeof_field(struct kvm_set_memory_attributes2, field)); \ +} while (0) + static long kvm_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) { @@ -5366,15 +5375,35 @@ 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_userspace_memory_region shouldn't be + * accessed, but avoid leaking kernel memory in case of a bug. + */ + memset(&mem, 0, sizeof(mem)); + size = sizeof(struct kvm_set_memory_attributes); + } else { + size = sizeof(struct kvm_set_memory_attributes2); + } + + /* Ensure the common parts of the two structs are identical. */ + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(slot); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(flags); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(guest_phys_addr); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(memory_size); + SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(userspace_addr);
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);