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SubjectRe: [PATCH v2 6/9] iommu/ioasid: Introduce notification APIs
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Hi Jacob,

On 9/10/20 12:58 AM, Jacob Pan wrote:
> On Tue, 1 Sep 2020 18:49:38 +0200
> Auger Eric <eric.auger@redhat.com> wrote:
>
>> Hi Jacob,
>>
>> On 8/22/20 6:35 AM, Jacob Pan wrote:
>>> Relations among IOASID users largely follow a publisher-subscriber
>>> pattern. E.g. to support guest SVA on Intel Scalable I/O
>>> Virtualization (SIOV) enabled platforms, VFIO, IOMMU, device
>>> drivers, KVM are all users of IOASIDs. When a state change occurs,
>>> VFIO publishes the change event that needs to be processed by other
>>> users/subscribers.
>>>
>>> This patch introduced two types of notifications: global and per
>>> ioasid_set. The latter is intended for users who only needs to
>>> handle events related to the IOASID of a given set.
>>> For more information, refer to the kernel documentation at
>>> Documentation/ioasid.rst.
>>>
>>> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
>>> Signed-off-by: Wu Hao <hao.wu@intel.com>
>>> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
>>> ---
>>> drivers/iommu/ioasid.c | 280
>>> ++++++++++++++++++++++++++++++++++++++++++++++++-
>>> include/linux/ioasid.h | 70 +++++++++++++ 2 files changed, 348
>>> insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
>>> index c0aef38a4fde..6ddc09a7fe74 100644
>>> --- a/drivers/iommu/ioasid.c
>>> +++ b/drivers/iommu/ioasid.c
>>> @@ -9,8 +9,35 @@
>>> #include <linux/spinlock.h>
>>> #include <linux/xarray.h>
>>> #include <linux/ioasid.h>
>>> +#include <linux/sched/mm.h>
>>>
>>> static DEFINE_XARRAY_ALLOC(ioasid_sets);
>>> +/*
>>> + * An IOASID could have multiple consumers where each consumeer
>>> may have
>> can have multiple consumers
> Sounds good, I used past tense to describe a possibility :)
>
>>> + * hardware contexts associated with IOASIDs.
>>> + * When a status change occurs, such as IOASID is being freed,
>>> notifier chains
>> s/such as IOASID is being freed/, like on IOASID deallocation,
> Better, will do.
>
>>> + * are used to keep the consumers in sync.
>>> + * This is a publisher-subscriber pattern where publisher can
>>> change the
>>> + * state of each IOASID, e.g. alloc/free, bind IOASID to a device
>>> and mm.
>>> + * On the other hand, subscribers gets notified for the state
>>> change and
>>> + * keep local states in sync.
>>> + *
>>> + * Currently, the notifier is global. A further optimization could
>>> be per
>>> + * IOASID set notifier chain.
>>> + */
>>> +static ATOMIC_NOTIFIER_HEAD(ioasid_chain);
>>> +
>>> +/* List to hold pending notification block registrations */
>>> +static LIST_HEAD(ioasid_nb_pending_list);
>>> +static DEFINE_SPINLOCK(ioasid_nb_lock);
>>> +struct ioasid_set_nb {
>>> + struct list_head list;
>>> + struct notifier_block *nb;
>>> + void *token;
>>> + struct ioasid_set *set;
>>> + bool active;
>>> +};
>>> +
>>> enum ioasid_state {
>>> IOASID_STATE_INACTIVE,
>>> IOASID_STATE_ACTIVE,
>>> @@ -394,6 +421,7 @@ EXPORT_SYMBOL_GPL(ioasid_find_by_spid);
>>> ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min,
>>> ioasid_t max, void *private)
>>> {
>>> + struct ioasid_nb_args args;
>>> struct ioasid_data *data;
>>> void *adata;
>>> ioasid_t id = INVALID_IOASID;
>>> @@ -445,8 +473,14 @@ ioasid_t ioasid_alloc(struct ioasid_set *set,
>>> ioasid_t min, ioasid_t max, goto exit_free;
>>> }
>>> set->nr_ioasids++;
>>> - goto done_unlock;
>>> + args.id = id;
>>> + /* Set private ID is not attached during allocation */
>>> + args.spid = INVALID_IOASID;
>>> + args.set = set;
>>> + atomic_notifier_call_chain(&set->nh, IOASID_ALLOC, &args);
>>>
>>> + spin_unlock(&ioasid_allocator_lock);
>>> + return id;
>> spurious change
> Good catch. should just goto done_unlock.
>
>>> exit_free:
>>> kfree(data);
>>> done_unlock:
>>> @@ -479,6 +513,7 @@ static void ioasid_do_free(struct ioasid_data
>>> *data)
>>> static void ioasid_free_locked(struct ioasid_set *set, ioasid_t
>>> ioasid) {
>>> + struct ioasid_nb_args args;
>>> struct ioasid_data *data;
>>>
>>> data = xa_load(&active_allocator->xa, ioasid);
>>> @@ -491,7 +526,16 @@ static void ioasid_free_locked(struct
>>> ioasid_set *set, ioasid_t ioasid) pr_warn("Cannot free IOASID %u
>>> due to set ownership\n", ioasid); return;
>>> }
>>> +
>> spurious new line
> got it
>
>>> data->state = IOASID_STATE_FREE_PENDING;
>>> + /* Notify all users that this IOASID is being freed */
>>> + args.id = ioasid;
>>> + args.spid = data->spid;
>>> + args.pdata = data->private;
>>> + args.set = data->set;
>>> + atomic_notifier_call_chain(&ioasid_chain, IOASID_FREE,
>>> &args);
>>> + /* Notify the ioasid_set for per set users */
>>> + atomic_notifier_call_chain(&set->nh, IOASID_FREE, &args);
>>>
>>> if (!refcount_dec_and_test(&data->users))
>>> return;
>> Shouldn't we call the notifier only when ref count == 0?
> Not in the current scheme. The idea is to notify all users the PASID is
> being freed, then each user can drop its reference. When refcount == 0,
> the PASID will be returned to the pool.

OK
>
>>> @@ -514,6 +558,28 @@ void ioasid_free(struct ioasid_set *set,
>>> ioasid_t ioasid) }
>>> EXPORT_SYMBOL_GPL(ioasid_free);
>>>
>>> +static void ioasid_add_pending_nb(struct ioasid_set *set)
>>> +{
>>> + struct ioasid_set_nb *curr;
>>> +
>>> + if (set->type != IOASID_SET_TYPE_MM)
>>> + return;
>>> +
>>> + /*
>>> + * Check if there are any pending nb requests for the
>>> given token, if so
>>> + * add them to the notifier chain.
>>> + */
>>> + spin_lock(&ioasid_nb_lock);
>>> + list_for_each_entry(curr, &ioasid_nb_pending_list, list) {
>>> + if (curr->token == set->token && !curr->active) {
>>> + atomic_notifier_chain_register(&set->nh,
>>> curr->nb);
>>> + curr->set = set;
>>> + curr->active = true;
>>> + }
>>> + }
>>> + spin_unlock(&ioasid_nb_lock);
>>> +}
>>> +
>>> /**
>>> * ioasid_alloc_set - Allocate a new IOASID set for a given token
>>> *
>>> @@ -601,6 +667,13 @@ struct ioasid_set *ioasid_alloc_set(void
>>> *token, ioasid_t quota, int type) sdata->quota = quota;
>>> sdata->sid = id;
>>> refcount_set(&sdata->ref, 1);
>>> + ATOMIC_INIT_NOTIFIER_HEAD(&sdata->nh);
>>> +
>>> + /*
>>> + * Check if there are any pending nb requests for the
>>> given token, if so
>>> + * add them to the notifier chain.
>>> + */
>>> + ioasid_add_pending_nb(sdata);
>>>
>>> /*
>>> * Per set XA is used to store private IDs within the set,
>>> get ready @@ -617,6 +690,30 @@ struct ioasid_set
>>> *ioasid_alloc_set(void *token, ioasid_t quota, int type) }
>>> EXPORT_SYMBOL_GPL(ioasid_alloc_set);
>>>
>>> +
>>> +/*
>>> + * ioasid_find_mm_set - Retrieve IOASID set with mm token
>>> + * Take a reference of the set if found.
>>> + */
>>> +static struct ioasid_set *ioasid_find_mm_set(struct mm_struct
>>> *token) +{
>>> + struct ioasid_set *sdata, *set = NULL;
>>> + unsigned long index;
>>> +
>>> + spin_lock(&ioasid_allocator_lock);
>>> +
>>> + xa_for_each(&ioasid_sets, index, sdata) {
>>> + if (sdata->type == IOASID_SET_TYPE_MM &&
>>> sdata->token == token) {
>>> + refcount_inc(&sdata->ref);
>>> + set = sdata;
>>> + goto exit_unlock;
>>> + }
>>> + }
>>> +exit_unlock:
>>> + spin_unlock(&ioasid_allocator_lock);
>>> + return set;
>>> +}
>>> +
>>> void ioasid_set_get_locked(struct ioasid_set *set)
>>> {
>>> if (WARN_ON(xa_load(&ioasid_sets, set->sid) != set)) {
>>> @@ -638,6 +735,8 @@ EXPORT_SYMBOL_GPL(ioasid_set_get);
>>>
>>> void ioasid_set_put_locked(struct ioasid_set *set)
>>> {
>>> + struct ioasid_nb_args args = { 0 };
>>> + struct ioasid_set_nb *curr;
>>> struct ioasid_data *entry;
>>> unsigned long index;
>>>
>>> @@ -673,8 +772,24 @@ void ioasid_set_put_locked(struct ioasid_set
>>> *set) done_destroy:
>>> /* Return the quota back to system pool */
>>> ioasid_capacity_avail += set->quota;
>>> - kfree_rcu(set, rcu);
>>>
>>> + /* Restore pending status of the set NBs */
>>> + spin_lock(&ioasid_nb_lock);
>>> + list_for_each_entry(curr, &ioasid_nb_pending_list, list) {
>>> + if (curr->token == set->token) {
>>> + if (curr->active)
>>> + curr->active = false;
>>> + else
>>> + pr_warn("Set token exists but not
>>> active!\n");
>>> + }
>>> + }
>>> + spin_unlock(&ioasid_nb_lock);
>>> +
>>> + args.set = set;
>>> + atomic_notifier_call_chain(&ioasid_chain, IOASID_SET_FREE,
>>> &args); +
>>> + kfree_rcu(set, rcu);
>>> + pr_debug("Set freed %d\n", set->sid);
>>> /*
>>> * Token got released right away after the ioasid_set is
>>> freed.
>>> * If a new set is created immediately with the newly
>>> released token, @@ -927,6 +1042,167 @@ void *ioasid_find(struct
>>> ioasid_set *set, ioasid_t ioasid, }
>>> EXPORT_SYMBOL_GPL(ioasid_find);
>>>
>>> +int ioasid_register_notifier(struct ioasid_set *set, struct
>>> notifier_block *nb) +{
>>> + if (set)
>>> + return atomic_notifier_chain_register(&set->nh,
>>> nb);
>>> + else
>>> + return
>>> atomic_notifier_chain_register(&ioasid_chain, nb); +}
>>> +EXPORT_SYMBOL_GPL(ioasid_register_notifier);
>>> +
>>> +void ioasid_unregister_notifier(struct ioasid_set *set,
>>> + struct notifier_block *nb)
>>> +{
>>> + struct ioasid_set_nb *curr;
>>> +
>>> + spin_lock(&ioasid_nb_lock);
>>> + /*
>>> + * Pending list is registered with a token without an
>>> ioasid_set,
>>> + * therefore should not be unregistered directly.
>>> + */
>>> + list_for_each_entry(curr, &ioasid_nb_pending_list, list) {
>>> + if (curr->nb == nb) {
>>> + pr_warn("Cannot unregister NB from pending
>>> list\n");
>>> + spin_unlock(&ioasid_nb_lock);
>>> + return;
>>> + }
>>> + }
>>> + spin_unlock(&ioasid_nb_lock);
>> is it safe to release the lock here? What does prevent another NB to
>> be added to ioasid_nb_pending_list after that?
> Another NB will not be the same one as this NB, which is being removed.
> I don't see any issues.
> The only reason we check the pending list is to make sure the NB on the
> pending list must be removed by ioasid_unregister_notifier_mm() API.
Hum you're right, sorry for the noise.

Thanks

Eric
>
>>> +
>>> + if (set)
>>> + atomic_notifier_chain_unregister(&set->nh, nb);
>>> + else
>>> + atomic_notifier_chain_unregister(&ioasid_chain,
>>> nb); +}
>>> +EXPORT_SYMBOL_GPL(ioasid_unregister_notifier);
>>> +
>>> +int ioasid_register_notifier_mm(struct mm_struct *mm, struct
>>> notifier_block *nb) +{
>>> + struct ioasid_set_nb *curr;
>>> + struct ioasid_set *set;
>>> + int ret = 0;
>>> +
>>> + if (!mm)
>>> + return -EINVAL;
>>> +
>>> + spin_lock(&ioasid_nb_lock);
>>> +
>>> + /* Check for duplicates, nb is unique per set */
>>> + list_for_each_entry(curr, &ioasid_nb_pending_list, list) {
>>> + if (curr->token == mm && curr->nb == nb) {
>>> + ret = -EBUSY;
>>> + goto exit_unlock;
>>> + }
>>> + }
>>> +
>>> + /* Check if the token has an existing set */
>>> + set = ioasid_find_mm_set(mm);
>>> + if (IS_ERR_OR_NULL(set)) {
>>> + /* Add to the rsvd list as inactive */
>>> + curr->active = false;
>>> + } else {
>>> + /* REVISIT: Only register empty set for now. Can
>>> add an option
>>> + * in the future to playback existing PASIDs.
>>> + */
>>> + if (set->nr_ioasids) {
>>> + pr_warn("IOASID set %d not empty\n",
>>> set->sid);
>>> + ret = -EBUSY;
>>> + goto exit_unlock;
>>> + }
>>> + curr = kzalloc(sizeof(*curr), GFP_ATOMIC);
>>> + if (!curr) {
>>> + ret = -ENOMEM;
>>> + goto exit_unlock;
>>> + }
>>> + curr->token = mm;
>>> + curr->nb = nb;
>>> + curr->active = true;
>>> + curr->set = set;
>>> +
>>> + /* Set already created, add to the notifier chain
>>> */
>>> + atomic_notifier_chain_register(&set->nh, nb);
>>> + /*
>>> + * Do not hold a reference, if the set gets
>>> destroyed, the nb
>>> + * entry will be marked inactive.
>>> + */
>>> + ioasid_set_put(set);
>>> + }
>>> +
>>> + list_add(&curr->list, &ioasid_nb_pending_list);
>>> +
>>> +exit_unlock:
>>> + spin_unlock(&ioasid_nb_lock);
>>> + return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(ioasid_register_notifier_mm);
>>> +
>>> +void ioasid_unregister_notifier_mm(struct mm_struct *mm, struct
>>> notifier_block *nb) +{
>>> + struct ioasid_set_nb *curr;
>>> +
>>> + spin_lock(&ioasid_nb_lock);
>>> + list_for_each_entry(curr, &ioasid_nb_pending_list, list) {
>>> + if (curr->token == mm && curr->nb == nb) {
>>> + list_del(&curr->list);
>>> + goto exit_free;
>>> + }
>>> + }
>>> + pr_warn("No ioasid set found for mm token %llx\n",
>>> (u64)mm);
>>> + goto done_unlock;
>>> +
>>> +exit_free:
>>> + if (curr->active) {
>>> + pr_debug("mm set active, unregister %llx\n",
>>> + (u64)mm);
>>> + atomic_notifier_chain_unregister(&curr->set->nh,
>>> nb);
>>> + }
>>> + kfree(curr);
>>> +done_unlock:
>>> + spin_unlock(&ioasid_nb_lock);
>>> + return;
>>> +}
>>> +EXPORT_SYMBOL_GPL(ioasid_unregister_notifier_mm);
>>> +
>>> +/**
>>> + * ioasid_notify - Send notification on a given IOASID for status
>>> change.
>>> + * Used by publishers when the status change may
>>> affect
>>> + * subscriber's internal state.
>>> + *
>>> + * @ioasid: The IOASID to which the notification will send
>>> + * @cmd: The notification event
>>> + * @flags: Special instructions, e.g. notify with a set or
>>> global
>>> + */
>>> +int ioasid_notify(ioasid_t ioasid, enum ioasid_notify_val cmd,
>>> unsigned int flags) +{
>>> + struct ioasid_data *ioasid_data;
>>> + struct ioasid_nb_args args = { 0 };
>>> + int ret = 0;
>>> +
>>> + spin_lock(&ioasid_allocator_lock);
>>> + ioasid_data = xa_load(&active_allocator->xa, ioasid);
>>> + if (!ioasid_data) {
>>> + pr_err("Trying to notify unknown IOASID %u\n",
>>> ioasid);
>>> + spin_unlock(&ioasid_allocator_lock);
>>> + return -EINVAL;
>>> + }
>>> +
>>> + args.id = ioasid;
>>> + args.set = ioasid_data->set;
>>> + args.pdata = ioasid_data->private;
>>> + args.spid = ioasid_data->spid;
>>> + if (flags & IOASID_NOTIFY_ALL) {
>>> + ret = atomic_notifier_call_chain(&ioasid_chain,
>>> cmd, &args);
>>> + } else if (flags & IOASID_NOTIFY_SET) {
>>> + ret =
>>> atomic_notifier_call_chain(&ioasid_data->set->nh,
>>> + cmd, &args);
>>> + }
>>> + spin_unlock(&ioasid_allocator_lock);
>>> +
>>> + return ret;
>>> +}
>>> +EXPORT_SYMBOL_GPL(ioasid_notify);
>>> +
>>> MODULE_AUTHOR("Jean-Philippe Brucker
>>> <jean-philippe.brucker@arm.com>"); MODULE_AUTHOR("Jacob Pan
>>> <jacob.jun.pan@linux.intel.com>"); MODULE_DESCRIPTION("IO Address
>>> Space ID (IOASID) allocator"); diff --git a/include/linux/ioasid.h
>>> b/include/linux/ioasid.h index d4b3e83672f6..572111cd3b4b 100644
>>> --- a/include/linux/ioasid.h
>>> +++ b/include/linux/ioasid.h
>>> @@ -23,6 +23,7 @@ enum ioasid_set_type {
>>> * struct ioasid_set - Meta data about ioasid_set
>>> * @type: Token types and other features
>>> * @token: Unique to identify an IOASID set
>>> + * @nh: Notifier for IOASID events within the set
>> list of notifiers private to that set?
> Sounds more accurate.
>
>>> * @xa: XArray to store ioasid_set private IDs, can
>>> be used for
>>> * guest-host IOASID mapping, or just a private
>>> IOASID namespace.
>>> * @quota: Max number of IOASIDs can be allocated within
>>> the set @@ -32,6 +33,7 @@ enum ioasid_set_type {
>>> */
>>> struct ioasid_set {
>>> void *token;
>>> + struct atomic_notifier_head nh;
>>> struct xarray xa;
>>> int type;
>>> int quota;
>>> @@ -56,6 +58,49 @@ struct ioasid_allocator_ops {
>>> void *pdata;
>>> };
>>>
>>> +/* Notification data when IOASID status changed */
>>> +enum ioasid_notify_val {
>>> + IOASID_ALLOC = 1,
>>> + IOASID_FREE,
>>> + IOASID_BIND,
>>> + IOASID_UNBIND,
>>> + IOASID_SET_ALLOC,
>>> + IOASID_SET_FREE,
>>> +};
>>> +
>>> +#define IOASID_NOTIFY_ALL BIT(0)
>>> +#define IOASID_NOTIFY_SET BIT(1)
>>> +/**
>>> + * enum ioasid_notifier_prios - IOASID event notification order
>>> + *
>>> + * When status of an IOASID changes, users might need to take
>>> actions to
>>> + * reflect the new state. For example, when an IOASID is freed due
>>> to
>>> + * exception, the hardware context in virtual CPU, DMA device, and
>>> IOMMU
>>> + * shall be cleared and drained. Order is required to prevent life
>>> cycle
>>> + * problems.
>>> + */
>>> +enum ioasid_notifier_prios {
>>> + IOASID_PRIO_LAST,
>>> + IOASID_PRIO_DEVICE,
>>> + IOASID_PRIO_IOMMU,
>>> + IOASID_PRIO_CPU,
>>> +};
>>> +
>>> +/**
>>> + * struct ioasid_nb_args - Argument provided by IOASID core when
>>> notifier
>>> + * is called.
>>> + * @id: The IOASID being notified
>>> + * @spid: The set private ID associated with the IOASID
>>> + * @set: The IOASID set of @id
>>> + * @pdata: The private data attached to the IOASID
>>> + */
>>> +struct ioasid_nb_args {
>>> + ioasid_t id;
>>> + ioasid_t spid;
>>> + struct ioasid_set *set;
>>> + void *pdata;
>>> +};
>>> +
>>> #if IS_ENABLED(CONFIG_IOASID)
>>> void ioasid_install_capacity(ioasid_t total);
>>> ioasid_t ioasid_get_capacity(void);
>>> @@ -75,8 +120,16 @@ void *ioasid_find(struct ioasid_set *set,
>>> ioasid_t ioasid, bool (*getter)(void * int
>>> ioasid_attach_data(ioasid_t ioasid, void *data); int
>>> ioasid_attach_spid(ioasid_t ioasid, ioasid_t spid); ioasid_t
>>> ioasid_find_by_spid(struct ioasid_set *set, ioasid_t spid); +
>>> +int ioasid_register_notifier(struct ioasid_set *set,
>>> + struct notifier_block *nb);
>>> +void ioasid_unregister_notifier(struct ioasid_set *set,
>>> + struct notifier_block *nb);
>>> +
>>> int ioasid_register_allocator(struct ioasid_allocator_ops
>>> *allocator); void ioasid_unregister_allocator(struct
>>> ioasid_allocator_ops *allocator); +
>>> +int ioasid_notify(ioasid_t ioasid, enum ioasid_notify_val cmd,
>>> unsigned int flags); void ioasid_is_in_set(struct ioasid_set *set,
>>> ioasid_t ioasid); int ioasid_get(struct ioasid_set *set, ioasid_t
>>> ioasid); int ioasid_get_locked(struct ioasid_set *set, ioasid_t
>>> ioasid); @@ -85,6 +138,9 @@ void ioasid_put_locked(struct
>>> ioasid_set *set, ioasid_t ioasid); int
>>> ioasid_set_for_each_ioasid(struct ioasid_set *sdata, void
>>> (*fn)(ioasid_t id, void *data), void *data);
>>> +int ioasid_register_notifier_mm(struct mm_struct *mm, struct
>>> notifier_block *nb); +void ioasid_unregister_notifier_mm(struct
>>> mm_struct *mm, struct notifier_block *nb); +
>>> #else /* !CONFIG_IOASID */
>>> static inline void ioasid_install_capacity(ioasid_t total)
>>> {
>>> @@ -124,6 +180,20 @@ static inline void *ioasid_find(struct
>>> ioasid_set *set, ioasid_t ioasid, bool (* return NULL;
>>> }
>>>
>>> +static inline int ioasid_register_notifier(struct notifier_block
>>> *nb) +{
>>> + return -ENOTSUPP;
>>> +}
>>> +
>>> +static inline void ioasid_unregister_notifier(struct
>>> notifier_block *nb) +{
>>> +}
>>> +
>>> +static inline int ioasid_notify(ioasid_t ioasid, enum
>>> ioasid_notify_val cmd, unsigned int flags) +{
>>> + return -ENOTSUPP;
>>> +}
>>> +
>>> static inline int ioasid_register_allocator(struct
>>> ioasid_allocator_ops *allocator) {
>>> return -ENOTSUPP;
>>>
>> Thanks
>>
>> Eric
>>
>> _______________________________________________
>> iommu mailing list
>> iommu@lists.linux-foundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>
> [Jacob Pan]
>

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