[PATCH 2/4] KVM: add KVM_GUEST_MEMFD_POPULATE ioctl for guest_memfd

Nikita Kalyazin
2024-10-24T09:54:58Z

The ioctl populates guest_memfd with userspace-provided data.

Signed-off-by: Nikita Kalyazin <kalyazin@amazon.com>
---
include/linux/kvm_host.h | 3 +++
include/uapi/linux/kvm.h | 9 +++++++++
virt/kvm/guest_memfd.c | 7 +++++++
virt/kvm/kvm_main.c | 10 ++++++++++
4 files changed, 29 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index db567d26f7b9..5b0347783598 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2505,6 +2505,9 @@ typedef int (*kvm_gmem_populate_cb)(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,

long kvm_gmem_populate(struct kvm *kvm, gfn_t gfn, void __user *src, long npages,
kvm_gmem_populate_cb post_populate, void *opaque);
+
+int kvm_gmem_guest_memfd_populate(struct kvm *kvm,
+ struct kvm_guest_memfd_populate *populate);
#endif

#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_INVALIDATE
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 637efc055145..5d8073de0d96 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1573,4 +1573,13 @@ struct kvm_pre_fault_memory {
__u64 padding[5];
};

+struct kvm_guest_memfd_populate {
+ __u64 gpa;
+ __u64 size;
+ void __user *from;
+ __u64 flags;
+};
+
+#define KVM_GUEST_MEMFD_POPULATE _IOW(KVMIO, 0xd6, struct kvm_guest_memfd_populate)
+
#endif /* __LINUX_KVM_H */
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 954312fac462..08630b87f0e3 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -720,4 +720,11 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
return ret && !i ? ret : i;
}
EXPORT_SYMBOL_GPL(kvm_gmem_populate);
+
+int kvm_gmem_guest_memfd_populate(struct kvm *kvm,
+ struct kvm_guest_memfd_populate *populate)
+{
+ return kvm_gmem_populate(kvm, populate->gpa >> PAGE_SHIFT, populate->from,
+ populate->size >> PAGE_SHIFT, kvm_gmem_post_populate_generic, NULL);
+}
#endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 05cbb2548d99..e5bd2c0031bf 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -5383,6 +5383,16 @@ static long kvm_vm_ioctl(struct file *filp,
r = kvm_gmem_create(kvm, &guest_memfd);
break;
}
+ case KVM_GUEST_MEMFD_POPULATE: {
+ struct kvm_guest_memfd_populate populate;
+
+ r = -EFAULT;
+ if (copy_from_user(&populate, argp, sizeof(populate)))
+ goto out;
+
+ r = kvm_gmem_guest_memfd_populate(kvm, &populate);
+ break;
+ }
#endif
default:
r = kvm_arch_vm_ioctl(filp, ioctl, arg);
--
2.40.1