On Mon, Jun 08, 2026 at 04:42:21PM +0200, Jörg Rödel wrote:
> From: Paolo Bonzini <[email protected]>
>
> Add a new VM ioctl to create a new plane. It returns a new file
> descriptor which supports per-plane ioctls.
>
> Signed-off-by: Paolo Bonzini <[email protected]>
> Co-developed-by: Joerg Roedel <[email protected]>
> Signed-off-by: Joerg Roedel <[email protected]>
> ---
> include/uapi/linux/kvm.h | 2 ++
> virt/kvm/kvm_main.c | 75 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 77 insertions(+)
>
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 813f964a6dc1..24e34b8e4819 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1355,6 +1355,8 @@ struct kvm_s390_keyop {
> #define KVM_GET_DEVICE_ATTR _IOW(KVMIO, 0xe2, struct kvm_device_attr)
> #define KVM_HAS_DEVICE_ATTR _IOW(KVMIO, 0xe3, struct kvm_device_attr)
>
> +#define KVM_CREATE_PLANE _IO(KVMIO, 0xe4)
> +
> /*
> * ioctls for vcpu fds
> */
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 5a0277e2ac7c..03a44ff62f0f 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4843,6 +4843,34 @@ static long kvm_vcpu_compat_ioctl(struct file *filp,
> }
> #endif
>
> +static long kvm_plane_ioctl(struct file *filp, unsigned int ioctl,
> + unsigned long arg)
> +{
> + struct kvm_plane *plane = filp->private_data;
> +
> + if (plane->kvm->mm != current->mm || plane->kvm->vm_dead)
> + return -EIO;
> +
> + switch (ioctl) {
> + default:
> + return -ENOTTY;
> + }
> +}
> +
> +static int kvm_plane_release(struct inode *inode, struct file *filp)
> +{
> + struct kvm_plane *plane = filp->private_data;
> +
> + kvm_put_kvm(plane->kvm);
> + return 0;
> +}
> +
> +static struct file_operations kvm_plane_fops = {
> + .unlocked_ioctl = kvm_plane_ioctl,
> + .release = kvm_plane_release,
> + KVM_COMPAT(kvm_plane_ioctl),
> +};
> +
> static int kvm_device_mmap(struct file *filp, struct vm_area_struct *vma)
> {
> struct kvm_device *dev = filp->private_data;
> @@ -5288,6 +5316,49 @@ static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
> return fd;
> }
>
> +static int kvm_vm_ioctl_create_plane(struct kvm *kvm, unsigned id)
> +{
> + struct kvm_plane *plane;
> + struct file *file;
> + int r, fd;
> +
> + if (id >= kvm_arch_max_planes(kvm) ||
> + WARN_ON_ONCE(id >= KVM_MAX_PLANES))
> + return -EINVAL;
> +
> + guard(mutex)(&kvm->lock);
> + if (kvm->planes[id])
> + return -EEXIST;
> +
> + fd = get_unused_fd_flags(O_CLOEXEC);
> + if (fd < 0)
> + return fd;
> +
> + plane = kvm_create_plane(kvm, id);
> + if (!plane) {
> + r = -ENOMEM;
> + goto put_fd;
> + }
> +
> + kvm_get_kvm(kvm);
> + file = anon_inode_getfile("kvm-plane", &kvm_plane_fops, plane, O_RDWR);
> + if (IS_ERR(file)) {
> + r = PTR_ERR(file);
> + goto put_kvm;
> + }
> +
> + fd_install(fd, file);
> + return fd;
> +
> +put_kvm:
> + kvm_put_kvm(kvm);
> + kvm_destroy_one_plane(plane);
I believe shashiko is right here, and I don't see it changed in a later
patch: kvm->planes[id] will still point to the now-freed plane.
Probably best if kvm_destroy_one_plane(plane) sets that to NULL itself
after freeing the plane.
> +put_fd:
> + put_unused_fd(fd);
> + return r;
> +}
> +
> +
> #define SANITY_CHECK_MEM_REGION_FIELD(field)
> \
> do {
> \
> BUILD_BUG_ON(offsetof(struct kvm_userspace_memory_region, field) !=
> \
> @@ -5306,6 +5377,9 @@ static long kvm_vm_ioctl(struct file *filp,
> if (kvm->mm != current->mm || kvm->vm_dead)
> return -EIO;
> switch (ioctl) {
> + case KVM_CREATE_PLANE:
> + r = kvm_vm_ioctl_create_plane(kvm, arg);
> + break;
> case KVM_CREATE_VCPU:
> r = kvm_vm_ioctl_create_vcpu(kvm, arg);
> break;
> @@ -6676,6 +6750,7 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align,
> struct module *module)
> kvm_chardev_ops.owner = module;
> kvm_vm_fops.owner = module;
> kvm_vcpu_fops.owner = module;
> + kvm_plane_fops.owner = module;
> kvm_device_fops.owner = module;
>
> kvm_preempt_ops.sched_in = kvm_sched_in;
> --
> 2.53.0
>
