On Fri, 19 Jun 2026 13:41:22 +0100
Adrián Larumbe <[email protected]> wrote:
> When a VM is created, caller has to specify the range of the address space
> carve-out set aside for mapping kernel BO's. That means vm_bind mappings of
> UM-exposed BO's should not intersect with that region, but at the moment
> we're not checking this.
>
> At first, I thought of giving these values to drm_gpuvm_init() through its
> reserve_{offset, range} arguments, but it turns out that is meant for VM
> address spans that are not managed through the usual drm_gpuvm split/merge
> circuit, so storing the end of the user VA range at VM creation time and
> doing a quick check in the vm_bind ioctl path was the simplest workaround.
>
> Signed-off-by: Adrián Larumbe <[email protected]>
Reviewed-by: Boris Brezillon <[email protected]>
> ---
> drivers/gpu/drm/panthor/panthor_mmu.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c
> b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 31cc57029c12..a8de4fe6b231 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -310,6 +310,9 @@ struct panthor_vm {
> u64 end;
> } kernel_auto_va;
>
> + /** @user_va_end: Last VA in the address range VM users can map objects
> against. */
> + u64 user_va_end;
> +
> /** @as: Address space related fields. */
> struct {
> /**
> @@ -2893,6 +2896,8 @@ panthor_vm_create(struct panthor_device *ptdev, bool
> for_mcu,
> va_range = full_va_range;
> }
>
> + vm->user_va_end = kernel_va_start - 1;
> +
> mutex_init(&vm->mm_lock);
> drm_mm_init(&vm->mm, kernel_va_start, kernel_va_size);
> vm->kernel_auto_va.start = auto_kernel_va_start;
> @@ -2981,6 +2986,10 @@ panthor_vm_bind_prepare_op_ctx(struct drm_file *file,
> if (!IS_ALIGNED(op->va | op->size | op->bo_offset, vm_pgsz))
> return -EINVAL;
>
> + /* We don't allow mappings that overlap with kbo's reserved range */
> + if (op->va + op->size > vm->user_va_end)
> + return -EINVAL;
> +
> switch (op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) {
> case DRM_PANTHOR_VM_BIND_OP_TYPE_MAP:
> if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) {
>
