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 <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 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