[PATCH 08/10] accel/ivpu: Disable buffer sharing among VPU contexts

[Jeffrey Hugo]

On 1/5/2024 4:22 AM, Jacek Lawrynowicz wrote:
> This was not supported properly. A buffer was imported to another VPU
> context as a separate buffer object with duplicated sgt.
> Both exported and imported buffers could be DMA mapped causing a double
> mapping on the same device.
> 
> Imported buffer from another VPU context will now have just reference
> increased and there will be a single sgt fixing above problem but
> buffers still can't be shared among VPU contexts because each context
> have its own MMU mapping and ivpu_bo supports only single MMU mapping.
> 
> The solution would be to use a mapping list as in panfrost or etnaviv
> drivers and it will be implemented in future if required.
> 
> Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz at linux.intel.com>
> ---
>   drivers/accel/ivpu/ivpu_gem.c | 44 +++++------------------------------
>   1 file changed, 6 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/accel/ivpu/ivpu_gem.c b/drivers/accel/ivpu/ivpu_gem.c
> index 4de454bfbf91..8cb4d337552e 100644
> --- a/drivers/accel/ivpu/ivpu_gem.c
> +++ b/drivers/accel/ivpu/ivpu_gem.c
> @@ -222,6 +222,12 @@ static int ivpu_bo_open(struct drm_gem_object *obj, struct drm_file *file)
>   	struct ivpu_bo *bo = to_ivpu_bo(obj);
>   	struct ivpu_addr_range *range;
>   
> +	if (bo->ctx) {
> +		ivpu_warn(vdev, "Can't add BO (vpu_addr 0x%llx) to ctx %u: already in ctx %u\n",
> +			  bo->vpu_addr, file_priv->ctx.id, bo->ctx->id);

Looks like the vpu_addr is being used as a unique identifier for the BO. 
  Is that really the best value to use?  Seems like if I want to attack 
another context, knowing the device address of something that context 
owns would be useful information.