/* $NetBSD: drm_vma_manager.c,v 1.3 2021/12/18 23:44:57 riastradh Exp $ */
// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
* 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 <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: drm_vma_manager.c,v 1.3 2021/12/18 23:44:57 riastradh Exp $");
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/rbtree.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <drm/drm_mm.h>
#include <drm/drm_vma_manager.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.
*
* 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().
*
* Additionally to offset management, the vma offset manager also handles access
* management. For every open-file context that is allowed to access a given
* node, you must call drm_vma_node_allow(). Otherwise, an mmap() call on this
* open-file with the offset of the node will fail with -EACCES. To revoke
* access again, use drm_vma_node_revoke(). However, the caller is responsible
* for destroying already existing mappings, if required.
*/
/**
* 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);
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)
{
drm_mm_takedown(&mgr->vm_addr_space_mm);
}
EXPORT_SYMBOL(drm_vma_offset_manager_destroy);
/**
* 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)
*
* 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).
*
* Note that before lookup the vma offset manager lookup lock must be acquired
* with drm_vma_offset_lock_lookup(). See there for an example. This can then be
* used to implement weakly referenced lookups using kref_get_unless_zero().
*
* 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);
*
* 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_locked(struct drm_vma_offset_manager *mgr,
unsigned long start,
unsigned long pages)
{
struct drm_mm_node *node, *best;
struct rb_node *iter;
unsigned long offset;
iter = mgr->vm_addr_space_mm.interval_tree.rb_root.rb_node;
best = NULL;
while (likely(iter)) {
node = rb_entry(iter, struct drm_mm_node, rb);
offset = 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->start + best->size;
if (offset < start + pages)
best = NULL;
}
if (!best)
return NULL;
return container_of(best, struct drm_vma_offset_node, vm_node);
}
EXPORT_SYMBOL(drm_vma_offset_lookup_locked);
/**
* 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 = 0;
write_lock(&mgr->vm_lock);
if (!drm_mm_node_allocated(&node->vm_node))
ret = drm_mm_insert_node(&mgr->vm_addr_space_mm,
&node->vm_node, pages);
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)) {
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);
/**
* drm_vma_node_allow - Add open-file to list of allowed users
* @node: Node to modify
* @tag: Tag of file to remove
*
* Add @tag to the list of allowed open-files for this node. If @tag is
* already on this list, the ref-count is incremented.
*
* The list of allowed-users is preserved across drm_vma_offset_add() and
* drm_vma_offset_remove() calls. You may even call it if the node is currently
* not added to any offset-manager.
*
* You must remove all open-files the same number of times as you added them
* before destroying the node. Otherwise, you will leak memory.
*
* This is locked against concurrent access internally.
*
* RETURNS:
* 0 on success, negative error code on internal failure (out-of-mem)
*/
int drm_vma_node_allow(struct drm_vma_offset_node *node, struct drm_file *tag)
{
struct rb_node **iter;
struct rb_node *parent = NULL;
struct drm_vma_offset_file *new, *entry;
int ret = 0;
/* Preallocate entry to avoid atomic allocations below. It is quite
* unlikely that an open-file is added twice to a single node so we
* don't optimize for this case. OOM is checked below only if the entry
* is actually used. */
new = kmalloc(sizeof(*entry), GFP_KERNEL);
write_lock(&node->vm_lock);
iter = &node->vm_files.rb_node;
while (likely(*iter)) {
parent = *iter;
entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb);
if (tag == entry->vm_tag) {
entry->vm_count++;
goto unlock;
} else if (tag > entry->vm_tag) {
iter = &(*iter)->rb_right;
} else {
iter = &(*iter)->rb_left;
}
}
if (!new) {
ret = -ENOMEM;
goto unlock;
}
new->vm_tag = tag;
new->vm_count = 1;
rb_link_node(&new->vm_rb, parent, iter);
rb_insert_color(&new->vm_rb, &node->vm_files);
new = NULL;
unlock:
write_unlock(&node->vm_lock);
kfree(new);
return ret;
}
EXPORT_SYMBOL(drm_vma_node_allow);
/**
* drm_vma_node_revoke - Remove open-file from list of allowed users
* @node: Node to modify
* @tag: Tag of file to remove
*
* Decrement the ref-count of @tag in the list of allowed open-files on @node.
* If the ref-count drops to zero, remove @tag from the list. You must call
* this once for every drm_vma_node_allow() on @tag.
*
* This is locked against concurrent access internally.
*
* If @tag is not on the list, nothing is done.
*/
void drm_vma_node_revoke(struct drm_vma_offset_node *node,
struct drm_file *tag)
{
struct drm_vma_offset_file *entry;
struct rb_node *iter;
write_lock(&node->vm_lock);
iter = node->vm_files.rb_node;
while (likely(iter)) {
entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
if (tag == entry->vm_tag) {
if (!--entry->vm_count) {
rb_erase(&entry->vm_rb, &node->vm_files);
kfree(entry);
}
break;
} else if (tag > entry->vm_tag) {
iter = iter->rb_right;
} else {
iter = iter->rb_left;
}
}
write_unlock(&node->vm_lock);
}
EXPORT_SYMBOL(drm_vma_node_revoke);
/**
* drm_vma_node_is_allowed - Check whether an open-file is granted access
* @node: Node to check
* @tag: Tag of file to remove
*
* Search the list in @node whether @tag is currently on the list of allowed
* open-files (see drm_vma_node_allow()).
*
* This is locked against concurrent access internally.
*
* RETURNS:
* true iff @filp is on the list
*/
bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,
struct drm_file *tag)
{
struct drm_vma_offset_file *entry;
struct rb_node *iter;
read_lock(&node->vm_lock);
iter = node->vm_files.rb_node;
while (likely(iter)) {
entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
if (tag == entry->vm_tag)
break;
else if (tag > entry->vm_tag)
iter = iter->rb_right;
else
iter = iter->rb_left;
}
read_unlock(&node->vm_lock);
return iter;
}
EXPORT_SYMBOL(drm_vma_node_is_allowed);