On Fri, 13 Sep 2024 13:27:22 +0200
Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> wrote:
> drm_gpuvm_bo_obtain_prealloc() will call drm_gpuvm_bo_put() on our
> pre-allocated BO if the <BO,VM> association exists. Given we
> only have one ref on preallocated_vm_bo, drm_gpuvm_bo_destroy() will
> be called immediately, and we have to hold the VM resv lock when
> calling this function.
>
> Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Queued to drm-misc-fixes.
> ---
> drivers/gpu/drm/panthor/panthor_mmu.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 37f1885c54c7..aa12ed2acfcf 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -1251,9 +1251,17 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
> goto err_cleanup;
> }
>
> + /* drm_gpuvm_bo_obtain_prealloc() will call drm_gpuvm_bo_put() on our
> + * pre-allocated BO if the <BO,VM> association exists. Given we
> + * only have one ref on preallocated_vm_bo, drm_gpuvm_bo_destroy() will
> + * be called immediately, and we have to hold the VM resv lock when
> + * calling this function.
> + */
> + dma_resv_lock(panthor_vm_resv(vm), NULL);
> mutex_lock(&bo->gpuva_list_lock);
> op_ctx->map.vm_bo = drm_gpuvm_bo_obtain_prealloc(preallocated_vm_bo);
> mutex_unlock(&bo->gpuva_list_lock);
> + dma_resv_unlock(panthor_vm_resv(vm));
>
> /* If the a vm_bo for this <VM,BO> combination exists, it already
> * retains a pin ref, and we can release the one we took earlier.
