Commit 17b226dc authored by Boris Brezillon's avatar Boris Brezillon Committed by Joerg Roedel
Browse files

iommu: Allow passing custom allocators to pgtable drivers 



This will be useful for GPU drivers who want to keep page tables in a
pool so they can:

- keep freed page tables in a free pool and speed-up upcoming page
  table allocations
- batch page table allocation instead of allocating one page at a time
- pre-reserve pages for page tables needed for map/unmap operations,
  to ensure map/unmap operations don't try to allocate memory in paths
  they're allowed to block or fail

It might also be valuable for other aspects of GPU and similar
use-cases, like fine-grained memory accounting and resource limiting.

We will extend the Arm LPAE format to support custom allocators in a
separate commit.

Signed-off-by: default avatarBoris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Reviewed-by: default avatarRobin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20231124142434.1577550-2-boris.brezillon@collabora.com


Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent e7080665

drivers/iommu/io-pgtable.c

+23 −0
Original line number Diff line number Diff line
@@ -34,6 +34,26 @@ io_pgtable_init_table[IO_PGTABLE_NUM_FMTS] = { 
#endif

};



static int check_custom_allocator(enum io_pgtable_fmt fmt,

				  struct io_pgtable_cfg *cfg)

{

	/* No custom allocator, no need to check the format. */

	if (!cfg->alloc && !cfg->free)

		return 0;



	/* When passing a custom allocator, both the alloc and free

	 * functions should be provided.

	 */

	if (!cfg->alloc || !cfg->free)

		return -EINVAL;



	/* Make sure the format supports custom allocators. */

	if (io_pgtable_init_table[fmt]->caps & IO_PGTABLE_CAP_CUSTOM_ALLOCATOR)

		return 0;



	return -EINVAL;

}



struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt,

					    struct io_pgtable_cfg *cfg,

					    void *cookie)
@@ -44,6 +64,9 @@ struct io_pgtable_ops *alloc_io_pgtable_ops(enum io_pgtable_fmt fmt, 
	if (fmt >= IO_PGTABLE_NUM_FMTS)

		return NULL;



	if (check_custom_allocator(fmt, cfg))

		return NULL;



	fns = io_pgtable_init_table[fmt];

	if (!fns)

		return NULL;

include/linux/io-pgtable.h

+34 −0
Original line number Diff line number Diff line
@@ -100,6 +100,30 @@ struct io_pgtable_cfg { 
	const struct iommu_flush_ops	*tlb;

	struct device			*iommu_dev;



	/**

	 * @alloc: Custom page allocator.

	 *

	 * Optional hook used to allocate page tables. If this function is NULL,

	 * @free must be NULL too.

	 *

	 * Memory returned should be zeroed and suitable for dma_map_single() and

	 * virt_to_phys().

	 *

	 * Not all formats support custom page allocators. Before considering

	 * passing a non-NULL value, make sure the chosen page format supports

	 * this feature.

	 */

	void *(*alloc)(void *cookie, size_t size, gfp_t gfp);



	/**

	 * @free: Custom page de-allocator.

	 *

	 * Optional hook used to free page tables allocated with the @alloc

	 * hook. Must be non-NULL if @alloc is not NULL, must be NULL

	 * otherwise.

	 */

	void (*free)(void *cookie, void *pages, size_t size);



	/* Low-level data specific to the table format */

	union {

		struct {
@@ -241,16 +265,26 @@ io_pgtable_tlb_add_page(struct io_pgtable *iop, 
		iop->cfg.tlb->tlb_add_page(gather, iova, granule, iop->cookie);

}



/**

 * enum io_pgtable_caps - IO page table backend capabilities.

 */

enum io_pgtable_caps {

	/** @IO_PGTABLE_CAP_CUSTOM_ALLOCATOR: Backend accepts custom page table allocators. */

	IO_PGTABLE_CAP_CUSTOM_ALLOCATOR = BIT(0),

};



/**

 * struct io_pgtable_init_fns - Alloc/free a set of page tables for a

 *                              particular format.

 *

 * @alloc: Allocate a set of page tables described by cfg.

 * @free:  Free the page tables associated with iop.

 * @caps:  Combination of @io_pgtable_caps flags encoding the backend capabilities.

 */

struct io_pgtable_init_fns {

	struct io_pgtable *(*alloc)(struct io_pgtable_cfg *cfg, void *cookie);

	void (*free)(struct io_pgtable *iop);

	u32 caps;

};



extern struct io_pgtable_init_fns io_pgtable_arm_32_lpae_s1_init_fns;