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![Jean-Philippe Brucker](/assets/img/avatar_default.png)
Let IOASID users take references to existing ioasids with ioasid_get(). ioasid_put() drops a reference and only frees the ioasid when its reference number is zero. It returns true if the ioasid was freed. For drivers that don't call ioasid_get(), ioasid_put() is the same as ioasid_free(). Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Reviewed-by: Eric Auger <eric.auger@redhat.com> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com> Link: https://lore.kernel.org/r/20201106155048.997886-2-jean-philippe@linaro.org Signed-off-by: Will Deacon <will@kernel.org>
452 lines
13 KiB
C
452 lines
13 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* I/O Address Space ID allocator. There is one global IOASID space, split into
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* subsets. Users create a subset with DECLARE_IOASID_SET, then allocate and
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* free IOASIDs with ioasid_alloc and ioasid_put.
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*/
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#include <linux/ioasid.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/xarray.h>
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struct ioasid_data {
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ioasid_t id;
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struct ioasid_set *set;
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void *private;
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struct rcu_head rcu;
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refcount_t refs;
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};
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/*
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* struct ioasid_allocator_data - Internal data structure to hold information
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* about an allocator. There are two types of allocators:
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*
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* - Default allocator always has its own XArray to track the IOASIDs allocated.
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* - Custom allocators may share allocation helpers with different private data.
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* Custom allocators that share the same helper functions also share the same
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* XArray.
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* Rules:
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* 1. Default allocator is always available, not dynamically registered. This is
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* to prevent race conditions with early boot code that want to register
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* custom allocators or allocate IOASIDs.
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* 2. Custom allocators take precedence over the default allocator.
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* 3. When all custom allocators sharing the same helper functions are
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* unregistered (e.g. due to hotplug), all outstanding IOASIDs must be
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* freed. Otherwise, outstanding IOASIDs will be lost and orphaned.
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* 4. When switching between custom allocators sharing the same helper
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* functions, outstanding IOASIDs are preserved.
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* 5. When switching between custom allocator and default allocator, all IOASIDs
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* must be freed to ensure unadulterated space for the new allocator.
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*
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* @ops: allocator helper functions and its data
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* @list: registered custom allocators
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* @slist: allocators share the same ops but different data
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* @flags: attributes of the allocator
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* @xa: xarray holds the IOASID space
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* @rcu: used for kfree_rcu when unregistering allocator
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*/
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struct ioasid_allocator_data {
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struct ioasid_allocator_ops *ops;
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struct list_head list;
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struct list_head slist;
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#define IOASID_ALLOCATOR_CUSTOM BIT(0) /* Needs framework to track results */
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unsigned long flags;
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struct xarray xa;
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struct rcu_head rcu;
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};
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static DEFINE_SPINLOCK(ioasid_allocator_lock);
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static LIST_HEAD(allocators_list);
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static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque);
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static void default_free(ioasid_t ioasid, void *opaque);
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static struct ioasid_allocator_ops default_ops = {
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.alloc = default_alloc,
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.free = default_free,
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};
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static struct ioasid_allocator_data default_allocator = {
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.ops = &default_ops,
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.flags = 0,
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.xa = XARRAY_INIT(ioasid_xa, XA_FLAGS_ALLOC),
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};
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static struct ioasid_allocator_data *active_allocator = &default_allocator;
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static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void *opaque)
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{
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ioasid_t id;
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if (xa_alloc(&default_allocator.xa, &id, opaque, XA_LIMIT(min, max), GFP_ATOMIC)) {
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pr_err("Failed to alloc ioasid from %d to %d\n", min, max);
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return INVALID_IOASID;
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}
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return id;
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}
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static void default_free(ioasid_t ioasid, void *opaque)
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{
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struct ioasid_data *ioasid_data;
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ioasid_data = xa_erase(&default_allocator.xa, ioasid);
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kfree_rcu(ioasid_data, rcu);
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}
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/* Allocate and initialize a new custom allocator with its helper functions */
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static struct ioasid_allocator_data *ioasid_alloc_allocator(struct ioasid_allocator_ops *ops)
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{
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struct ioasid_allocator_data *ia_data;
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ia_data = kzalloc(sizeof(*ia_data), GFP_ATOMIC);
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if (!ia_data)
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return NULL;
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xa_init_flags(&ia_data->xa, XA_FLAGS_ALLOC);
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INIT_LIST_HEAD(&ia_data->slist);
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ia_data->flags |= IOASID_ALLOCATOR_CUSTOM;
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ia_data->ops = ops;
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/* For tracking custom allocators that share the same ops */
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list_add_tail(&ops->list, &ia_data->slist);
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return ia_data;
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}
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static bool use_same_ops(struct ioasid_allocator_ops *a, struct ioasid_allocator_ops *b)
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{
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return (a->free == b->free) && (a->alloc == b->alloc);
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}
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/**
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* ioasid_register_allocator - register a custom allocator
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* @ops: the custom allocator ops to be registered
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*
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* Custom allocators take precedence over the default xarray based allocator.
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* Private data associated with the IOASID allocated by the custom allocators
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* are managed by IOASID framework similar to data stored in xa by default
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* allocator.
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*
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* There can be multiple allocators registered but only one is active. In case
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* of runtime removal of a custom allocator, the next one is activated based
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* on the registration ordering.
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*
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* Multiple allocators can share the same alloc() function, in this case the
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* IOASID space is shared.
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*/
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int ioasid_register_allocator(struct ioasid_allocator_ops *ops)
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{
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struct ioasid_allocator_data *ia_data;
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struct ioasid_allocator_data *pallocator;
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int ret = 0;
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spin_lock(&ioasid_allocator_lock);
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ia_data = ioasid_alloc_allocator(ops);
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if (!ia_data) {
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ret = -ENOMEM;
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goto out_unlock;
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}
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/*
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* No particular preference, we activate the first one and keep
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* the later registered allocators in a list in case the first one gets
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* removed due to hotplug.
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*/
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if (list_empty(&allocators_list)) {
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WARN_ON(active_allocator != &default_allocator);
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/* Use this new allocator if default is not active */
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if (xa_empty(&active_allocator->xa)) {
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rcu_assign_pointer(active_allocator, ia_data);
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list_add_tail(&ia_data->list, &allocators_list);
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goto out_unlock;
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}
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pr_warn("Default allocator active with outstanding IOASID\n");
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ret = -EAGAIN;
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goto out_free;
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}
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/* Check if the allocator is already registered */
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list_for_each_entry(pallocator, &allocators_list, list) {
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if (pallocator->ops == ops) {
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pr_err("IOASID allocator already registered\n");
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ret = -EEXIST;
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goto out_free;
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} else if (use_same_ops(pallocator->ops, ops)) {
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/*
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* If the new allocator shares the same ops,
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* then they will share the same IOASID space.
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* We should put them under the same xarray.
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*/
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list_add_tail(&ops->list, &pallocator->slist);
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goto out_free;
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}
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}
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list_add_tail(&ia_data->list, &allocators_list);
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spin_unlock(&ioasid_allocator_lock);
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return 0;
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out_free:
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kfree(ia_data);
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out_unlock:
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spin_unlock(&ioasid_allocator_lock);
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return ret;
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}
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EXPORT_SYMBOL_GPL(ioasid_register_allocator);
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/**
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* ioasid_unregister_allocator - Remove a custom IOASID allocator ops
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* @ops: the custom allocator to be removed
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*
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* Remove an allocator from the list, activate the next allocator in
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* the order it was registered. Or revert to default allocator if all
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* custom allocators are unregistered without outstanding IOASIDs.
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*/
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void ioasid_unregister_allocator(struct ioasid_allocator_ops *ops)
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{
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struct ioasid_allocator_data *pallocator;
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struct ioasid_allocator_ops *sops;
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spin_lock(&ioasid_allocator_lock);
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if (list_empty(&allocators_list)) {
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pr_warn("No custom IOASID allocators active!\n");
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goto exit_unlock;
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}
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list_for_each_entry(pallocator, &allocators_list, list) {
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if (!use_same_ops(pallocator->ops, ops))
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continue;
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if (list_is_singular(&pallocator->slist)) {
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/* No shared helper functions */
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list_del(&pallocator->list);
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/*
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* All IOASIDs should have been freed before
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* the last allocator that shares the same ops
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* is unregistered.
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*/
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WARN_ON(!xa_empty(&pallocator->xa));
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if (list_empty(&allocators_list)) {
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pr_info("No custom IOASID allocators, switch to default.\n");
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rcu_assign_pointer(active_allocator, &default_allocator);
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} else if (pallocator == active_allocator) {
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rcu_assign_pointer(active_allocator,
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list_first_entry(&allocators_list,
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struct ioasid_allocator_data, list));
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pr_info("IOASID allocator changed");
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}
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kfree_rcu(pallocator, rcu);
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break;
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}
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/*
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* Find the matching shared ops to delete,
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* but keep outstanding IOASIDs
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*/
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list_for_each_entry(sops, &pallocator->slist, list) {
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if (sops == ops) {
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list_del(&ops->list);
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break;
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}
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}
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break;
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}
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exit_unlock:
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spin_unlock(&ioasid_allocator_lock);
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}
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EXPORT_SYMBOL_GPL(ioasid_unregister_allocator);
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/**
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* ioasid_set_data - Set private data for an allocated ioasid
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* @ioasid: the ID to set data
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* @data: the private data
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*
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* For IOASID that is already allocated, private data can be set
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* via this API. Future lookup can be done via ioasid_find.
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*/
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int ioasid_set_data(ioasid_t ioasid, void *data)
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{
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struct ioasid_data *ioasid_data;
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int ret = 0;
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spin_lock(&ioasid_allocator_lock);
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ioasid_data = xa_load(&active_allocator->xa, ioasid);
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if (ioasid_data)
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rcu_assign_pointer(ioasid_data->private, data);
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else
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ret = -ENOENT;
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spin_unlock(&ioasid_allocator_lock);
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/*
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* Wait for readers to stop accessing the old private data, so the
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* caller can free it.
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*/
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if (!ret)
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synchronize_rcu();
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return ret;
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}
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EXPORT_SYMBOL_GPL(ioasid_set_data);
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/**
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* ioasid_alloc - Allocate an IOASID
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* @set: the IOASID set
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* @min: the minimum ID (inclusive)
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* @max: the maximum ID (inclusive)
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* @private: data private to the caller
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*
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* Allocate an ID between @min and @max. The @private pointer is stored
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* internally and can be retrieved with ioasid_find().
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*
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* Return: the allocated ID on success, or %INVALID_IOASID on failure.
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*/
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ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
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void *private)
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{
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struct ioasid_data *data;
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void *adata;
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ioasid_t id;
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data = kzalloc(sizeof(*data), GFP_ATOMIC);
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if (!data)
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return INVALID_IOASID;
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data->set = set;
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data->private = private;
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refcount_set(&data->refs, 1);
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/*
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* Custom allocator needs allocator data to perform platform specific
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* operations.
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*/
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spin_lock(&ioasid_allocator_lock);
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adata = active_allocator->flags & IOASID_ALLOCATOR_CUSTOM ? active_allocator->ops->pdata : data;
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id = active_allocator->ops->alloc(min, max, adata);
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if (id == INVALID_IOASID) {
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pr_err("Failed ASID allocation %lu\n", active_allocator->flags);
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goto exit_free;
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}
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if ((active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) &&
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xa_alloc(&active_allocator->xa, &id, data, XA_LIMIT(id, id), GFP_ATOMIC)) {
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/* Custom allocator needs framework to store and track allocation results */
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pr_err("Failed to alloc ioasid from %d\n", id);
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active_allocator->ops->free(id, active_allocator->ops->pdata);
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goto exit_free;
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}
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data->id = id;
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spin_unlock(&ioasid_allocator_lock);
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return id;
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exit_free:
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spin_unlock(&ioasid_allocator_lock);
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kfree(data);
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return INVALID_IOASID;
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}
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EXPORT_SYMBOL_GPL(ioasid_alloc);
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/**
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* ioasid_get - obtain a reference to the IOASID
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*/
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void ioasid_get(ioasid_t ioasid)
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{
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struct ioasid_data *ioasid_data;
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spin_lock(&ioasid_allocator_lock);
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ioasid_data = xa_load(&active_allocator->xa, ioasid);
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if (ioasid_data)
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refcount_inc(&ioasid_data->refs);
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else
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WARN_ON(1);
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spin_unlock(&ioasid_allocator_lock);
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}
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EXPORT_SYMBOL_GPL(ioasid_get);
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/**
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* ioasid_put - Release a reference to an ioasid
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* @ioasid: the ID to remove
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*
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* Put a reference to the IOASID, free it when the number of references drops to
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* zero.
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*
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* Return: %true if the IOASID was freed, %false otherwise.
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*/
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bool ioasid_put(ioasid_t ioasid)
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{
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bool free = false;
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struct ioasid_data *ioasid_data;
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spin_lock(&ioasid_allocator_lock);
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ioasid_data = xa_load(&active_allocator->xa, ioasid);
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if (!ioasid_data) {
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pr_err("Trying to free unknown IOASID %u\n", ioasid);
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goto exit_unlock;
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}
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free = refcount_dec_and_test(&ioasid_data->refs);
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if (!free)
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goto exit_unlock;
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active_allocator->ops->free(ioasid, active_allocator->ops->pdata);
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/* Custom allocator needs additional steps to free the xa element */
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if (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) {
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ioasid_data = xa_erase(&active_allocator->xa, ioasid);
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kfree_rcu(ioasid_data, rcu);
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}
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exit_unlock:
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spin_unlock(&ioasid_allocator_lock);
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return free;
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}
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EXPORT_SYMBOL_GPL(ioasid_put);
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/**
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* ioasid_find - Find IOASID data
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* @set: the IOASID set
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* @ioasid: the IOASID to find
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* @getter: function to call on the found object
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*
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* The optional getter function allows to take a reference to the found object
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* under the rcu lock. The function can also check if the object is still valid:
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* if @getter returns false, then the object is invalid and NULL is returned.
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*
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* If the IOASID exists, return the private pointer passed to ioasid_alloc.
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* Private data can be NULL if not set. Return an error if the IOASID is not
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* found, or if @set is not NULL and the IOASID does not belong to the set.
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*/
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void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
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bool (*getter)(void *))
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{
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void *priv;
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struct ioasid_data *ioasid_data;
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struct ioasid_allocator_data *idata;
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rcu_read_lock();
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idata = rcu_dereference(active_allocator);
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ioasid_data = xa_load(&idata->xa, ioasid);
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if (!ioasid_data) {
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priv = ERR_PTR(-ENOENT);
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goto unlock;
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}
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if (set && ioasid_data->set != set) {
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/* data found but does not belong to the set */
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priv = ERR_PTR(-EACCES);
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goto unlock;
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}
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/* Now IOASID and its set is verified, we can return the private data */
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priv = rcu_dereference(ioasid_data->private);
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if (getter && !getter(priv))
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priv = NULL;
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unlock:
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rcu_read_unlock();
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return priv;
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}
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EXPORT_SYMBOL_GPL(ioasid_find);
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MODULE_AUTHOR("Jean-Philippe Brucker <jean-philippe.brucker@arm.com>");
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MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>");
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MODULE_DESCRIPTION("IO Address Space ID (IOASID) allocator");
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MODULE_LICENSE("GPL");
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