Hi Jacob, On 4/24/19 1:31 AM, Jacob Pan wrote: > Sometimes, IOASID allocation must be handled by platform specific > code. The use cases are guest vIOMMU and pvIOMMU where IOASIDs need > to be allocated by the host via enlightened or paravirt interfaces. > > This patch adds an extension to the IOASID allocator APIs such that > platform drivers can register a custom allocator, possibly at boot > time, to take over the allocation. Xarray is still used for tracking > and searching purposes internal to the IOASID code. Private data of > an IOASID can also be set after the allocation. > > There can be multiple custom allocators registered but only one is > used at a time. In case of hot removal of devices that provides the > allocator, all IOASIDs must be freed prior to unregistering the > allocator. Default XArray based allocator cannot be mixed with > custom allocators, i.e. custom allocators will not be used if there > are outstanding IOASIDs allocated by the default XA allocator.
What's the exact use case behind allowing several custom IOASID allocators to be registered? > > Signed-off-by: Jacob Pan <[email protected]> > --- > drivers/base/ioasid.c | 182 > ++++++++++++++++++++++++++++++++++++++++++++++--- > include/linux/ioasid.h | 15 +++- > 2 files changed, 187 insertions(+), 10 deletions(-) > > diff --git a/drivers/base/ioasid.c b/drivers/base/ioasid.c > index c4012aa..5cb36a4 100644 > --- a/drivers/base/ioasid.c > +++ b/drivers/base/ioasid.c > @@ -17,6 +17,120 @@ struct ioasid_data { > }; > > static DEFINE_XARRAY_ALLOC(ioasid_xa); > +static DEFINE_MUTEX(ioasid_allocator_lock); > +static struct ioasid_allocator *ioasid_allocator; A more explicit name may be chosen. If I understand correctly that's the active_custom_allocator > + > +static LIST_HEAD(custom_allocators); > +/* > + * A flag to track if ioasid default allocator already been used, this will is already in use? > + * prevent custom allocator from being used. The reason is that custom > allocator s/The reason is that custom allocator/The reason is that custom allocators > + * must have unadulterated space to track private data with xarray, there > cannot > + * be a mix been default and custom allocated IOASIDs. > + */ > +static int default_allocator_used; > + > +/** > + * ioasid_register_allocator - register a custom allocator > + * @allocator: the custom allocator to be registered > + * > + * Custom allocator take precedence over the default xarray based allocator. > + * Private data associated with the ASID are managed by ASID common code > + * similar to data stored in xa. > + * > + * There can be multiple allocators registered but only one is active. In > case > + * of runtime removal of an custom allocator, the next one is activated based > + * on the registration ordering. This last sentence may be moved to the unregister() kerneldoc > + */ > +int ioasid_register_allocator(struct ioasid_allocator *allocator) > +{ > + struct ioasid_allocator *pallocator; > + int ret = 0; > + > + if (!allocator) > + return -EINVAL; > + > + mutex_lock(&ioasid_allocator_lock); > + if (list_empty(&custom_allocators)) > + ioasid_allocator = allocator; The fact the first registered custom allocator gets automatically active was not obvious to me and may deserve a comment. > + else { > + /* Check if the allocator is already registered */ > + list_for_each_entry(pallocator, &custom_allocators, list) { > + if (pallocator == allocator) { > + pr_err("IOASID allocator already exist\n"); s/exist/registered? > + ret = -EEXIST; > + goto out_unlock; > + } > + } > + } > + list_add_tail(&allocator->list, &custom_allocators); > + > +out_unlock: > + mutex_unlock(&ioasid_allocator_lock); > + return ret; > +} > +EXPORT_SYMBOL_GPL(ioasid_register_allocator); > + > +/** > + * ioasid_unregister_allocator - Remove a custom IOASID allocator > + * @allocator: the custom allocator to be removed > + * > + * Remove an allocator from the list, activate the next allocator in > + * the order it was registration. > + */ > +void ioasid_unregister_allocator(struct ioasid_allocator *allocator) > +{ > + if (!allocator) > + return; > + > + if (list_empty(&custom_allocators)) { > + pr_warn("No custom IOASID allocators active!\n"); s/active/registered? > + return; > + } > + > + mutex_lock(&ioasid_allocator_lock); > + list_del(&allocator->list); > + if (list_empty(&custom_allocators)) { > + pr_info("No custom IOASID allocators\n"); > + /* > + * All IOASIDs should have been freed before the last allocator > + * is unregistered. > + */ > + BUG_ON(!xa_empty(&ioasid_xa)); At this stage it is difficult to assess whether using a BUG_ON() is safe here. Who is responsible for freeing the IOASIDs? > + ioasid_allocator = NULL; > + } else if (allocator == ioasid_allocator) { > + ioasid_allocator = list_entry(&custom_allocators, struct > ioasid_allocator, list); > + pr_info("IOASID allocator changed"); > + } > + mutex_unlock(&ioasid_allocator_lock); > +} > +EXPORT_SYMBOL_GPL(ioasid_unregister_allocator); > + > +/** > + * ioasid_set_data - Set private data for an allocated ioasid > + * @ioasid: the ID to set data > + * @data: the private data > + * > + * For IOASID that is already allocated, private data can be set > + * via this API. Future lookup can be done via ioasid_find. > + */ > +int ioasid_set_data(ioasid_t ioasid, void *data) > +{ > + struct ioasid_data *ioasid_data; > + int ret = 0; > + > + ioasid_data = xa_load(&ioasid_xa, ioasid); > + if (ioasid_data) > + ioasid_data->private = data; > + else > + ret = -ENOENT; > + > + /* getter may use the private data */ > + synchronize_rcu(); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(ioasid_set_data); > + > /** > * ioasid_alloc - Allocate an IOASID > * @set: the IOASID set > @@ -31,7 +145,7 @@ static DEFINE_XARRAY_ALLOC(ioasid_xa); > ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max, > void *private) > { > - int id = -1; > + int id = INVALID_IOASID; > struct ioasid_data *data; > > data = kzalloc(sizeof(*data), GFP_KERNEL); > @@ -40,14 +154,37 @@ ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t > min, ioasid_t max, > > data->set = set; > data->private = private; > + > + /* > + * Use custom allocator if available, otherwise use default. > + * However, if there are active IOASIDs already been allocated by > default > + * allocator, custom allocator cannot be used. > + */ > + if (!default_allocator_used && ioasid_allocator) { > + mutex_lock(&ioasid_allocator_lock); > + id = ioasid_allocator->alloc(min, max, ioasid_allocator->pdata); > + mutex_unlock(&ioasid_allocator_lock); > + if (id == INVALID_IOASID) { > + pr_err("Failed ASID allocation by custom allocator\n"); > + goto exit_free; > + } > + /* > + * Use XA to manage private data also sanitiy check custom> + > * allocator for duplicates. s/data also sanitiy check/data, also sanity check > + */ > + min = id; > + max = id + 1; > + } else > + default_allocator_used = 1; shouldn't default_allocator_used be protected as well? > + > if (xa_alloc(&ioasid_xa, &id, data, XA_LIMIT(min, max), GFP_KERNEL)) { > pr_err("Failed to alloc ioasid from %d to %d\n", min, max); > goto exit_free; > } > - > data->id = id; wouldn't it be possible to integrate the default io asid allocator as any custom allocator, ie. implement an alloc callback using xa_alloc. Then the active io allocator could be either a custom or a default one. > + > exit_free: > - if (id < 0) { > + if (id < 0 || id == INVALID_IOASID) { > kfree(data); > return INVALID_IOASID; > } > @@ -59,12 +196,29 @@ EXPORT_SYMBOL_GPL(ioasid_alloc); > * ioasid_free - Free an IOASID > * @ioasid: the ID to remove > */ > -void ioasid_free(ioasid_t ioasid) > +int ioasid_free(ioasid_t ioasid) > { > struct ioasid_data *ioasid_data; > + int ret = 0; > + > + if (ioasid_allocator) { > + mutex_lock(&ioasid_allocator_lock); > + ret = ioasid_allocator->free(ioasid, ioasid_allocator->pdata); > + mutex_unlock(&ioasid_allocator_lock); > + } > + if (ret) { > + pr_err("ioasid %d custom allocator free failed\n", ioasid); > + return ret; > + } > > ioasid_data = xa_erase(&ioasid_xa, ioasid); > + > kfree_rcu(ioasid_data, rcu); > + > + if (xa_empty(&ioasid_xa)) > + default_allocator_used = 0; > + > + return ret; > } > EXPORT_SYMBOL_GPL(ioasid_free); > > @@ -79,7 +233,8 @@ EXPORT_SYMBOL_GPL(ioasid_free); > * if @getter returns false, then the object is invalid and NULL is returned. > * > * If the IOASID has been allocated for this set, return the private pointer > - * passed to ioasid_alloc. Otherwise return NULL. > + * passed to ioasid_alloc. Private data can be NULL if not set. Return an > error > + * if the IOASID is not found or not belong to the set. s/not belong/does not belong > */ > void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, > bool (*getter)(void *)) > @@ -89,11 +244,20 @@ void *ioasid_find(struct ioasid_set *set, ioasid_t > ioasid, > > rcu_read_lock(); > ioasid_data = xa_load(&ioasid_xa, ioasid); > - if (ioasid_data && ioasid_data->set == set) { > - priv = ioasid_data->private; > - if (getter && !getter(priv)) > - priv = NULL; > + if (!ioasid_data) { > + priv = ERR_PTR(-ENOENT); > + goto unlock; > + } > + if (set && ioasid_data->set != set) { > + /* data found but does not belong to the set */ > + priv = ERR_PTR(-EACCES); > + goto unlock; > } > + /* Now IOASID and its set is verified, we can return the private data */ > + priv = ioasid_data->private; > + if (getter && !getter(priv)) > + priv = NULL; > +unlock: > rcu_read_unlock(); > > return priv; > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h > index 6f3655a..e773c13 100644 > --- a/include/linux/ioasid.h > +++ b/include/linux/ioasid.h > @@ -5,20 +5,33 @@ > #define INVALID_IOASID ((ioasid_t)-1) > typedef unsigned int ioasid_t; > typedef int (*ioasid_iter_t)(ioasid_t ioasid, void *private, void *data); > +typedef ioasid_t (*ioasid_alloc_fn_t)(ioasid_t min, ioasid_t max, void > *data); > +typedef int (*ioasid_free_fn_t)(ioasid_t ioasid, void *data); > > struct ioasid_set { > int dummy; > }; > > +struct ioasid_allocator { > + ioasid_alloc_fn_t alloc; > + ioasid_free_fn_t free; > + void *pdata; > + struct list_head list; > +}; > + > #define DECLARE_IOASID_SET(name) struct ioasid_set name = { 0 } > > #ifdef CONFIG_IOASID > ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max, > void *private); > -void ioasid_free(ioasid_t ioasid); > +int ioasid_free(ioasid_t ioasid); you need to change the definition for the !CONFIG_IOASID case too > > void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, > bool (*getter)(void *)); > +int ioasid_register_allocator(struct ioasid_allocator *allocator); > +void ioasid_unregister_allocator(struct ioasid_allocator *allocator); > + > +int ioasid_set_data(ioasid_t ioasid, void *data); > > #else /* !CONFIG_IOASID */ > static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, Just to make sure, don't you need to define the new functions if !CONFIG_IOASID? Thanks Eric > _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
