Re: [PATCH v1 7/9] drm/panthor: Split panthor_vm_prepare_map_op_ctx() to prepare for reclaim

[Liviu Dudau <liviu.dudau@arm.com>]

On Fri, Jan 09, 2026 at 02:07:59PM +0100, Boris Brezillon wrote:
> We're gonna need just the page table reservation logic when we restore
> evicted BO mappings, so let's prepare for that by extracting the
> op_ctx init and page table pre-allocation into separate helpers.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c | 70 ++++++++++++++++-----------
>  1 file changed, 42 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index c323b7123713..3290e0b5facb 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -1170,6 +1170,45 @@ panthor_vm_op_ctx_prealloc_vmas(struct panthor_vm_op_ctx *op_ctx)
>  	return 0;
>  }
>  
> +static void panthor_vm_init_op_ctx(struct panthor_vm_op_ctx *op_ctx,
> +				   u64 size, u64 va, u32 flags)
> +{
> +	memset(op_ctx, 0, sizeof(*op_ctx));
> +	op_ctx->flags = flags;
> +	op_ctx->va.range = size;
> +	op_ctx->va.addr = va;
> +}
> +
> +static int panthor_vm_op_ctx_prealloc_pts(struct panthor_vm_op_ctx *op_ctx)
> +{
> +	u64 size = op_ctx->va.range;
> +	u64 va = op_ctx->va.addr;
> +	int ret;
> +
> +	/* L1, L2 and L3 page tables.
> +	 * We could optimize L3 allocation by iterating over the sgt and merging
> +	 * 2M contiguous blocks, but it's simpler to over-provision and return
> +	 * the pages if they're not used.
> +	 */
> +	u64 pt_count = ((ALIGN(va + size, 1ull << 39) - ALIGN_DOWN(va, 1ull << 39)) >> 39) +
> +		       ((ALIGN(va + size, 1ull << 30) - ALIGN_DOWN(va, 1ull << 30)) >> 30) +
> +		       ((ALIGN(va + size, 1ull << 21) - ALIGN_DOWN(va, 1ull << 21)) >> 21);
> +
> +	op_ctx->rsvd_page_tables.pages = kcalloc(pt_count,
> +						 sizeof(*op_ctx->rsvd_page_tables.pages),
> +						 GFP_KERNEL);
> +	if (!op_ctx->rsvd_page_tables.pages)
> +		return -ENOMEM;
> +
> +	ret = kmem_cache_alloc_bulk(pt_cache, GFP_KERNEL, pt_count,
> +				    op_ctx->rsvd_page_tables.pages);
> +	op_ctx->rsvd_page_tables.count = ret;
> +	if (ret != pt_count)
> +		return -ENOMEM;
> +
> +	return 0;
> +}
> +
>  #define PANTHOR_VM_BIND_OP_MAP_FLAGS \
>  	(DRM_PANTHOR_VM_BIND_OP_MAP_READONLY | \
>  	 DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC | \
> @@ -1185,7 +1224,6 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  {
>  	struct drm_gpuvm_bo *preallocated_vm_bo;
>  	struct sg_table *sgt = NULL;
> -	u64 pt_count;
>  	int ret;
>  
>  	if (!bo)
> @@ -1204,10 +1242,7 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  	    bo->exclusive_vm_root_gem != panthor_vm_root_gem(vm))
>  		return -EINVAL;
>  
> -	memset(op_ctx, 0, sizeof(*op_ctx));
> -	op_ctx->flags = flags;
> -	op_ctx->va.range = size;
> -	op_ctx->va.addr = va;
> +	panthor_vm_init_op_ctx(op_ctx, size, va, flags);
>  
>  	ret = panthor_vm_op_ctx_prealloc_vmas(op_ctx);
>  	if (ret)
> @@ -1250,30 +1285,9 @@ static int panthor_vm_prepare_map_op_ctx(struct panthor_vm_op_ctx *op_ctx,
>  
>  	op_ctx->map.bo_offset = offset;
>  
> -	/* L1, L2 and L3 page tables.
> -	 * We could optimize L3 allocation by iterating over the sgt and merging
> -	 * 2M contiguous blocks, but it's simpler to over-provision and return
> -	 * the pages if they're not used.
> -	 */
> -	pt_count = ((ALIGN(va + size, 1ull << 39) - ALIGN_DOWN(va, 1ull << 39)) >> 39) +
> -		   ((ALIGN(va + size, 1ull << 30) - ALIGN_DOWN(va, 1ull << 30)) >> 30) +
> -		   ((ALIGN(va + size, 1ull << 21) - ALIGN_DOWN(va, 1ull << 21)) >> 21);
> -
> -	op_ctx->rsvd_page_tables.pages = kcalloc(pt_count,
> -						 sizeof(*op_ctx->rsvd_page_tables.pages),
> -						 GFP_KERNEL);
> -	if (!op_ctx->rsvd_page_tables.pages) {
> -		ret = -ENOMEM;
> +	ret = panthor_vm_op_ctx_prealloc_pts(op_ctx);
> +	if (ret)
>  		goto err_cleanup;
> -	}
> -
> -	ret = kmem_cache_alloc_bulk(pt_cache, GFP_KERNEL, pt_count,
> -				    op_ctx->rsvd_page_tables.pages);
> -	op_ctx->rsvd_page_tables.count = ret;
> -	if (ret != pt_count) {
> -		ret = -ENOMEM;
> -		goto err_cleanup;
> -	}
>  
>  	/* Insert BO into the extobj list last, when we know nothing can fail. */
>  	dma_resv_lock(panthor_vm_resv(vm), NULL);
> -- 
> 2.52.0
>