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Commit fe3078fa authored by David Herrmann's avatar David Herrmann Committed by Dave Airlie
Browse files

drm: add unified vma offset manager 



If we want to map GPU memory into user-space, we need to linearize the
addresses to not confuse mm-core. Currently, GEM and TTM both implement
their own offset-managers to assign a pgoff to each object for user-space
CPU access. GEM uses a hash-table, TTM uses an rbtree.

This patch provides a unified implementation that can be used to replace
both. TTM allows partial mmaps with a given offset, so we cannot use
hashtables as the start address may not be known at mmap time. Hence, we
use the rbtree-implementation of TTM.

We could easily update drm_mm to use an rbtree instead of a linked list
for it's object list and thus drop the rbtree from the vma-manager.
However, this would slow down drm_mm object allocation for all other
use-cases (rbtree insertion) and add another 4-8 bytes to each mm node.
Hence, use the separate tree but allow for later migration.

This is a rewrite of the 2012-proposal by David Airlie <airlied@linux.ie>

v2:
 - fix Docbook integration
 - drop drm_mm_node_linked() and use drm_mm_node_allocated()
 - remove unjustified likely/unlikely usage (but keep for rbtree paths)
 - remove BUG_ON() as drm_mm already does that
 - clarify page-based vs. byte-based addresses
 - use drm_vma_node_reset() for initialization, too
v4:
 - allow external locking via drm_vma_offset_un/lock_lookup()
 - add locked lookup helper drm_vma_offset_lookup_locked()
v5:
 - fix drm_vma_offset_lookup() to correctly validate range-mismatches
   (fix (offset > start + pages))
 - fix drm_vma_offset_exact_lookup() to actually do what it says
 - remove redundant vm_pages member (add drm_vma_node_size() helper)
 - remove unneeded goto
 - fix documentation

Signed-off-by: default avatarDavid Herrmann <dh.herrmann@gmail.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: default avatarDave Airlie <airlied@gmail.com>
parent 85d9cb41

Documentation/DocBook/drm.tmpl

+6 −0
Original line number Diff line number Diff line
@@ -2212,6 +2212,12 @@ void intel_crt_init(struct drm_device *dev) 
!Iinclude/drm/drm_rect.h

!Edrivers/gpu/drm/drm_rect.c

    </sect2>

    <sect2>

      <title>VMA Offset Manager</title>

!Pdrivers/gpu/drm/drm_vma_manager.c vma offset manager

!Edrivers/gpu/drm/drm_vma_manager.c

!Iinclude/drm/drm_vma_manager.h

    </sect2>

  </sect1>



  <!-- Internals: kms properties -->

drivers/gpu/drm/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -13,7 +13,7 @@ drm-y := drm_auth.o drm_buffer.o drm_bufs.o drm_cache.o \ 
		drm_crtc.o drm_modes.o drm_edid.o \

		drm_info.o drm_debugfs.o drm_encoder_slave.o \

		drm_trace_points.o drm_global.o drm_prime.o \

		drm_rect.o

		drm_rect.o drm_vma_manager.o



drm-$(CONFIG_COMPAT) += drm_ioc32.o

drm-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_gem_cma_helper.o

drivers/gpu/drm/drm_vma_manager.c

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+281 −0
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA

 * Copyright (c) 2012 David Airlie <airlied@linux.ie>

 * Copyright (c) 2013 David Herrmann <dh.herrmann@gmail.com>

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL

 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR

 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,

 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

 * OTHER DEALINGS IN THE SOFTWARE.

 */



#include <drm/drmP.h>

#include <drm/drm_mm.h>

#include <drm/drm_vma_manager.h>

#include <linux/mm.h>

#include <linux/module.h>

#include <linux/rbtree.h>

#include <linux/slab.h>

#include <linux/spinlock.h>

#include <linux/types.h>



/**

 * DOC: vma offset manager

 *

 * The vma-manager is responsible to map arbitrary driver-dependent memory

 * regions into the linear user address-space. It provides offsets to the

 * caller which can then be used on the address_space of the drm-device. It

 * takes care to not overlap regions, size them appropriately and to not

 * confuse mm-core by inconsistent fake vm_pgoff fields.

 * Drivers shouldn't use this for object placement in VMEM. This manager should

 * only be used to manage mappings into linear user-space VMs.

 *

 * We use drm_mm as backend to manage object allocations. But it is highly

 * optimized for alloc/free calls, not lookups. Hence, we use an rb-tree to

 * speed up offset lookups.

 *

 * You must not use multiple offset managers on a single address_space.

 * Otherwise, mm-core will be unable to tear down memory mappings as the VM will

 * no longer be linear. Please use VM_NONLINEAR in that case and implement your

 * own offset managers.

 *

 * This offset manager works on page-based addresses. That is, every argument

 * and return code (with the exception of drm_vma_node_offset_addr()) is given

 * in number of pages, not number of bytes. That means, object sizes and offsets

 * must always be page-aligned (as usual).

 * If you want to get a valid byte-based user-space address for a given offset,

 * please see drm_vma_node_offset_addr().

 */



/**

 * drm_vma_offset_manager_init - Initialize new offset-manager

 * @mgr: Manager object

 * @page_offset: Offset of available memory area (page-based)

 * @size: Size of available address space range (page-based)

 *

 * Initialize a new offset-manager. The offset and area size available for the

 * manager are given as @page_offset and @size. Both are interpreted as

 * page-numbers, not bytes.

 *

 * Adding/removing nodes from the manager is locked internally and protected

 * against concurrent access. However, node allocation and destruction is left

 * for the caller. While calling into the vma-manager, a given node must

 * always be guaranteed to be referenced.

 */

void drm_vma_offset_manager_init(struct drm_vma_offset_manager *mgr,

				 unsigned long page_offset, unsigned long size)

{

	rwlock_init(&mgr->vm_lock);

	mgr->vm_addr_space_rb = RB_ROOT;

	drm_mm_init(&mgr->vm_addr_space_mm, page_offset, size);

}

EXPORT_SYMBOL(drm_vma_offset_manager_init);



/**

 * drm_vma_offset_manager_destroy() - Destroy offset manager

 * @mgr: Manager object

 *

 * Destroy an object manager which was previously created via

 * drm_vma_offset_manager_init(). The caller must remove all allocated nodes

 * before destroying the manager. Otherwise, drm_mm will refuse to free the

 * requested resources.

 *

 * The manager must not be accessed after this function is called.

 */

void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr)

{

	/* take the lock to protect against buggy drivers */

	write_lock(&mgr->vm_lock);

	drm_mm_takedown(&mgr->vm_addr_space_mm);

	write_unlock(&mgr->vm_lock);

}

EXPORT_SYMBOL(drm_vma_offset_manager_destroy);



/**

 * drm_vma_offset_lookup() - Find node in offset space

 * @mgr: Manager object

 * @start: Start address for object (page-based)

 * @pages: Size of object (page-based)

 *

 * Find a node given a start address and object size. This returns the _best_

 * match for the given node. That is, @start may point somewhere into a valid

 * region and the given node will be returned, as long as the node spans the

 * whole requested area (given the size in number of pages as @pages).

 *

 * RETURNS:

 * Returns NULL if no suitable node can be found. Otherwise, the best match

 * is returned. It's the caller's responsibility to make sure the node doesn't

 * get destroyed before the caller can access it.

 */

struct drm_vma_offset_node *drm_vma_offset_lookup(struct drm_vma_offset_manager *mgr,

						  unsigned long start,

						  unsigned long pages)

{

	struct drm_vma_offset_node *node;



	read_lock(&mgr->vm_lock);

	node = drm_vma_offset_lookup_locked(mgr, start, pages);

	read_unlock(&mgr->vm_lock);



	return node;

}

EXPORT_SYMBOL(drm_vma_offset_lookup);



/**

 * drm_vma_offset_lookup_locked() - Find node in offset space

 * @mgr: Manager object

 * @start: Start address for object (page-based)

 * @pages: Size of object (page-based)

 *

 * Same as drm_vma_offset_lookup() but requires the caller to lock offset lookup

 * manually. See drm_vma_offset_lock_lookup() for an example.

 *

 * RETURNS:

 * Returns NULL if no suitable node can be found. Otherwise, the best match

 * is returned.

 */

struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,

							 unsigned long start,

							 unsigned long pages)

{

	struct drm_vma_offset_node *node, *best;

	struct rb_node *iter;

	unsigned long offset;



	iter = mgr->vm_addr_space_rb.rb_node;

	best = NULL;



	while (likely(iter)) {

		node = rb_entry(iter, struct drm_vma_offset_node, vm_rb);

		offset = node->vm_node.start;

		if (start >= offset) {

			iter = iter->rb_right;

			best = node;

			if (start == offset)

				break;

		} else {

			iter = iter->rb_left;

		}

	}



	/* verify that the node spans the requested area */

	if (best) {

		offset = best->vm_node.start + best->vm_node.size;

		if (offset < start + pages)

			best = NULL;

	}



	return best;

}

EXPORT_SYMBOL(drm_vma_offset_lookup_locked);



/* internal helper to link @node into the rb-tree */

static void _drm_vma_offset_add_rb(struct drm_vma_offset_manager *mgr,

				   struct drm_vma_offset_node *node)

{

	struct rb_node **iter = &mgr->vm_addr_space_rb.rb_node;

	struct rb_node *parent = NULL;

	struct drm_vma_offset_node *iter_node;



	while (likely(*iter)) {

		parent = *iter;

		iter_node = rb_entry(*iter, struct drm_vma_offset_node, vm_rb);



		if (node->vm_node.start < iter_node->vm_node.start)

			iter = &(*iter)->rb_left;

		else if (node->vm_node.start > iter_node->vm_node.start)

			iter = &(*iter)->rb_right;

		else

			BUG();

	}



	rb_link_node(&node->vm_rb, parent, iter);

	rb_insert_color(&node->vm_rb, &mgr->vm_addr_space_rb);

}



/**

 * drm_vma_offset_add() - Add offset node to manager

 * @mgr: Manager object

 * @node: Node to be added

 * @pages: Allocation size visible to user-space (in number of pages)

 *

 * Add a node to the offset-manager. If the node was already added, this does

 * nothing and return 0. @pages is the size of the object given in number of

 * pages.

 * After this call succeeds, you can access the offset of the node until it

 * is removed again.

 *

 * If this call fails, it is safe to retry the operation or call

 * drm_vma_offset_remove(), anyway. However, no cleanup is required in that

 * case.

 *

 * @pages is not required to be the same size as the underlying memory object

 * that you want to map. It only limits the size that user-space can map into

 * their address space.

 *

 * RETURNS:

 * 0 on success, negative error code on failure.

 */

int drm_vma_offset_add(struct drm_vma_offset_manager *mgr,

		       struct drm_vma_offset_node *node, unsigned long pages)

{

	int ret;



	write_lock(&mgr->vm_lock);



	if (drm_mm_node_allocated(&node->vm_node)) {

		ret = 0;

		goto out_unlock;

	}



	ret = drm_mm_insert_node_generic(&mgr->vm_addr_space_mm,

					 &node->vm_node, pages, 0, 0);

	if (ret)

		goto out_unlock;



	_drm_vma_offset_add_rb(mgr, node);



out_unlock:

	write_unlock(&mgr->vm_lock);

	return ret;

}

EXPORT_SYMBOL(drm_vma_offset_add);



/**

 * drm_vma_offset_remove() - Remove offset node from manager

 * @mgr: Manager object

 * @node: Node to be removed

 *

 * Remove a node from the offset manager. If the node wasn't added before, this

 * does nothing. After this call returns, the offset and size will be 0 until a

 * new offset is allocated via drm_vma_offset_add() again. Helper functions like

 * drm_vma_node_start() and drm_vma_node_offset_addr() will return 0 if no

 * offset is allocated.

 */

void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,

			   struct drm_vma_offset_node *node)

{

	write_lock(&mgr->vm_lock);



	if (drm_mm_node_allocated(&node->vm_node)) {

		rb_erase(&node->vm_rb, &mgr->vm_addr_space_rb);

		drm_mm_remove_node(&node->vm_node);

		memset(&node->vm_node, 0, sizeof(node->vm_node));

	}



	write_unlock(&mgr->vm_lock);

}

EXPORT_SYMBOL(drm_vma_offset_remove);

include/drm/drm_vma_manager.h

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+202 −0
Original line number Diff line number Diff line 
#ifndef __DRM_VMA_MANAGER_H__

#define __DRM_VMA_MANAGER_H__



/*

 * Copyright (c) 2013 David Herrmann <dh.herrmann@gmail.com>

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL

 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR

 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,

 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

 * OTHER DEALINGS IN THE SOFTWARE.

 */



#include <drm/drm_mm.h>

#include <linux/module.h>

#include <linux/rbtree.h>

#include <linux/spinlock.h>

#include <linux/types.h>



struct drm_vma_offset_node {

	struct drm_mm_node vm_node;

	struct rb_node vm_rb;

};



struct drm_vma_offset_manager {

	rwlock_t vm_lock;

	struct rb_root vm_addr_space_rb;

	struct drm_mm vm_addr_space_mm;

};



void drm_vma_offset_manager_init(struct drm_vma_offset_manager *mgr,

				 unsigned long page_offset, unsigned long size);

void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr);



struct drm_vma_offset_node *drm_vma_offset_lookup(struct drm_vma_offset_manager *mgr,

						  unsigned long start,

						  unsigned long pages);

struct drm_vma_offset_node *drm_vma_offset_lookup_locked(struct drm_vma_offset_manager *mgr,

							   unsigned long start,

							   unsigned long pages);

int drm_vma_offset_add(struct drm_vma_offset_manager *mgr,

		       struct drm_vma_offset_node *node, unsigned long pages);

void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,

			   struct drm_vma_offset_node *node);



/**

 * drm_vma_offset_exact_lookup() - Look up node by exact address

 * @mgr: Manager object

 * @start: Start address (page-based, not byte-based)

 * @pages: Size of object (page-based)

 *

 * Same as drm_vma_offset_lookup() but does not allow any offset into the node.

 * It only returns the exact object with the given start address.

 *

 * RETURNS:

 * Node at exact start address @start.

 */

static inline struct drm_vma_offset_node *

drm_vma_offset_exact_lookup(struct drm_vma_offset_manager *mgr,

			    unsigned long start,

			    unsigned long pages)

{

	struct drm_vma_offset_node *node;



	node = drm_vma_offset_lookup(mgr, start, pages);

	return (node && node->vm_node.start == start) ? node : NULL;

}



/**

 * drm_vma_offset_lock_lookup() - Lock lookup for extended private use

 * @mgr: Manager object

 *

 * Lock VMA manager for extended lookups. Only *_locked() VMA function calls

 * are allowed while holding this lock. All other contexts are blocked from VMA

 * until the lock is released via drm_vma_offset_unlock_lookup().

 *

 * Use this if you need to take a reference to the objects returned by

 * drm_vma_offset_lookup_locked() before releasing this lock again.

 *

 * This lock must not be used for anything else than extended lookups. You must

 * not call any other VMA helpers while holding this lock.

 *

 * Note: You're in atomic-context while holding this lock!

 *

 * Example:

 *   drm_vma_offset_lock_lookup(mgr);

 *   node = drm_vma_offset_lookup_locked(mgr);

 *   if (node)

 *       kref_get_unless_zero(container_of(node, sth, entr));

 *   drm_vma_offset_unlock_lookup(mgr);

 */

static inline void drm_vma_offset_lock_lookup(struct drm_vma_offset_manager *mgr)

{

	read_lock(&mgr->vm_lock);

}



/**

 * drm_vma_offset_unlock_lookup() - Unlock lookup for extended private use

 * @mgr: Manager object

 *

 * Release lookup-lock. See drm_vma_offset_lock_lookup() for more information.

 */

static inline void drm_vma_offset_unlock_lookup(struct drm_vma_offset_manager *mgr)

{

	read_unlock(&mgr->vm_lock);

}



/**

 * drm_vma_node_reset() - Initialize or reset node object

 * @node: Node to initialize or reset

 *

 * Reset a node to its initial state. This must be called if @node isn't

 * already cleared (eg., via kzalloc) before using it with any VMA offset

 * manager.

 *

 * This must not be called on an already allocated node, or you will leak

 * memory.

 */

static inline void drm_vma_node_reset(struct drm_vma_offset_node *node)

{

	memset(node, 0, sizeof(*node));

}



/**

 * drm_vma_node_start() - Return start address for page-based addressing

 * @node: Node to inspect

 *

 * Return the start address of the given node. This can be used as offset into

 * the linear VM space that is provided by the VMA offset manager. Note that

 * this can only be used for page-based addressing. If you need a proper offset

 * for user-space mappings, you must apply "<< PAGE_SHIFT" or use the

 * drm_vma_node_offset_addr() helper instead.

 *

 * RETURNS:

 * Start address of @node for page-based addressing. 0 if the node does not

 * have an offset allocated.

 */

static inline unsigned long drm_vma_node_start(struct drm_vma_offset_node *node)

{

	return node->vm_node.start;

}



/**

 * drm_vma_node_size() - Return size (page-based)

 * @node: Node to inspect

 *

 * Return the size as number of pages for the given node. This is the same size

 * that was passed to drm_vma_offset_add(). If no offset is allocated for the

 * node, this is 0.

 *

 * RETURNS:

 * Size of @node as number of pages. 0 if the node does not have an offset

 * allocated.

 */

static inline unsigned long drm_vma_node_size(struct drm_vma_offset_node *node)

{

	return node->vm_node.size;

}



/**

 * drm_vma_node_has_offset() - Check whether node is added to offset manager

 * @node: Node to be checked

 *

 * RETURNS:

 * true iff the node was previously allocated an offset and added to

 * an vma offset manager.

 */

static inline bool drm_vma_node_has_offset(struct drm_vma_offset_node *node)

{

	return drm_mm_node_allocated(&node->vm_node);

}



/**

 * drm_vma_node_offset_addr() - Return sanitized offset for user-space mmaps

 * @node: Linked offset node

 *

 * Same as drm_vma_node_start() but returns the address as a valid offset that

 * can be used for user-space mappings during mmap().

 * This must not be called on unlinked nodes.

 *

 * RETURNS:

 * Offset of @node for byte-based addressing. 0 if the node does not have an

 * object allocated.

 */

static inline __u64 drm_vma_node_offset_addr(struct drm_vma_offset_node *node)

{

	return ((__u64)node->vm_node.start) << PAGE_SHIFT;

}



#endif /* __DRM_VMA_MANAGER_H__ */