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
Signed-off-by: David Herrmann dh.herrmann@gmail.com --- drivers/gpu/drm/Makefile | 2 +- drivers/gpu/drm/drm_vma_manager.c | 224 ++++++++++++++++++++++++++++++++++++++ include/drm/drm_vma_manager.h | 107 ++++++++++++++++++ 3 files changed, 332 insertions(+), 1 deletion(-) create mode 100644 drivers/gpu/drm/drm_vma_manager.c create mode 100644 include/drm/drm_vma_manager.h
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile index 1c9f2439..f8851cc 100644 --- a/drivers/gpu/drm/Makefile +++ b/drivers/gpu/drm/Makefile @@ -12,7 +12,7 @@ drm-y := drm_auth.o drm_buffer.o drm_bufs.o drm_cache.o \ drm_platform.o drm_sysfs.o drm_hashtab.o drm_mm.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_trace_points.o drm_global.o drm_prime.o drm_vma_manager.o
drm-$(CONFIG_COMPAT) += drm_ioc32.o drm-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_gem_cma_helper.o diff --git a/drivers/gpu/drm/drm_vma_manager.c b/drivers/gpu/drm/drm_vma_manager.c new file mode 100644 index 0000000..c28639f --- /dev/null +++ b/drivers/gpu/drm/drm_vma_manager.c @@ -0,0 +1,224 @@ +/* + * 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> + +/** @file drm_vma_manager.c + * + * 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. + * + * 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. + */ + +/** drm_vma_offset_manager_init() + * + * 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 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) +{ + BUG_ON(!drm_mm_clean(&mgr->vm_addr_space_mm)); + + /* 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 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 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, *best; + struct rb_node *iter; + unsigned long offset; + + read_lock(&mgr->vm_lock); + + 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 (likely(best)) { + offset = best->vm_node.start + best->vm_pages; + if (offset > start + pages) + best = NULL; + } + + read_unlock(&mgr->vm_lock); + + return best; +} +EXPORT_SYMBOL(drm_vma_offset_lookup); + +/* 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 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. + */ +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 (unlikely(drm_mm_node_linked(&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 (unlikely(ret)) + goto out_reset; + + node->vm_pages = pages; + _drm_vma_offset_add_rb(mgr, node); + goto out_unlock; + +out_reset: + /* we don't know what happened to @node->vm_node, so clear it */ + drm_vma_node_reset(node); +out_unlock: + write_unlock(&mgr->vm_lock); + return ret; +} +EXPORT_SYMBOL(drm_vma_offset_add); + +/** drm_vma_offset_remove() + * + * Remove a node from the offset manager. If the node wasn't added before, this + * does nothing. After this call returns, the offset of the node must be not + * accessed, anymore. + * It is safe to add the node via drm_vma_offset_add() again. + */ +void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr, + struct drm_vma_offset_node *node) +{ + if (unlikely(!drm_mm_node_linked(&node->vm_node))) + return; + + write_lock(&mgr->vm_lock); + + rb_erase(&node->vm_rb, &mgr->vm_addr_space_rb); + drm_mm_remove_node(&node->vm_node); + drm_vma_node_reset(node); + + write_unlock(&mgr->vm_lock); +} +EXPORT_SYMBOL(drm_vma_offset_remove); diff --git a/include/drm/drm_vma_manager.h b/include/drm/drm_vma_manager.h new file mode 100644 index 0000000..8a1975c --- /dev/null +++ b/include/drm/drm_vma_manager.h @@ -0,0 +1,107 @@ +#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/drmP.h> +#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; + unsigned long vm_pages; +}; + +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); +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() + * + * Same as drm_vma_offset_lookup() but does not allow any offset but only + * returns the exact object with the given start address. + */ +static inline struct drm_vma_offset_node * +drm_vma_offset_exact_lookup(struct drm_vma_offset_manager *mgr, + unsigned long start) +{ + return drm_vma_offset_lookup(mgr, start, 1); +} + +/** drm_vma_node_reset() + * + * Reset a node to its initial state. + */ +static inline void drm_vma_node_reset(struct drm_vma_offset_node *node) +{ + memset(&node->vm_node, 0, sizeof(node->vm_node)); +} + +/** drm_vma_node_start() + * + * Return the start address of the given node as pfn. + */ +static inline unsigned long drm_vma_node_start(struct drm_vma_offset_node *node) +{ + return node->vm_node.start; +} + +/** drm_vma_node_has_offset() + * + * Return 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_linked(&node->vm_node); +} + +/** drm_vma_node_offset_addr() + * + * Same as drm_vma_node_start() but returns the address as a valid userspace + * address (instead of a pfn). + */ +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__ */