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@xxxxxxxx>
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
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
---
Documentation/DocBook/drm.tmpl | 6 +
drivers/gpu/drm/Makefile | 2 +-
drivers/gpu/drm/drm_vma_manager.c | 260 ++++++++++++++++++++++++++++++++++++++
include/drm/drm_vma_manager.h | 138 ++++++++++++++++++++
4 files changed, 405 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/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 4d54ac8..b02732d 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -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 -->
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 801bcaf..d943b94 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -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
diff --git a/drivers/gpu/drm/drm_vma_manager.c b/drivers/gpu/drm/drm_vma_manager.c
new file mode 100644
index 0000000..4b5f415
--- /dev/null
+++ b/drivers/gpu/drm/drm_vma_manager.c
@@ -0,0 +1,260 @@
+/*
+ * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
+ * Copyright (c) 2012 David Airlie <airlied@xxxxxxxx>
+ * Copyright (c) 2013 David Herrmann <dh.herrmann@xxxxxxxxx>
+ *
+ * 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 memory area (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, *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 (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 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;
+
+ node->vm_pages = pages;
+ _drm_vma_offset_add_rb(mgr, node);
+ goto out_unlock;
+
+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 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)
+{
+ 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));
+ node->vm_pages = 0;
+ }
+
+ 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..4fcc441
--- /dev/null
+++ b/include/drm/drm_vma_manager.h
@@ -0,0 +1,138 @@
+#ifndef __DRM_VMA_MANAGER_H__
+#define __DRM_VMA_MANAGER_H__
+
+/*
+ * Copyright (c) 2013 David Herrmann <dh.herrmann@xxxxxxxxx>
+ *
+ * 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;
+ 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() - Look up node by exact address
+ * @mgr: Manager object
+ * @start: Start address (page-based, not byte-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)
+{
+ return drm_vma_offset_lookup(mgr, start, 1);
+}
+
+/**
+ * drm_vma_node_reset() - Initialize or reset node object
+ * @node: Node to initialize or reset
+ *
+ * Reset a node to its initial state. You must call this before using @node 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_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__ */
--
1.8.3.2
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