Messages in this thread | | | From | "Tian, Kevin" <> | Subject | RE: [PATCH 08/10] iommu/ioasid: Introduce notifier APIs | Date | Sat, 28 Mar 2020 06:43:37 +0000 |
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> From: Jacob Pan <jacob.jun.pan@linux.intel.com> > Sent: Saturday, March 28, 2020 2:37 AM > > On Fri, 27 Mar 2020 10:03:26 +0000 > "Tian, Kevin" <kevin.tian@intel.com> wrote: > > > > From: Jacob Pan <jacob.jun.pan@linux.intel.com> > > > Sent: Thursday, March 26, 2020 1:55 AM > > > > > > IOASID users fit into the publisher-subscriber pattern, a system > > > wide blocking notifier chain can be used to inform subscribers of > > > state changes. Notifier mechanism also abstracts publisher from > > > knowing the private context each subcriber may have. > > > > > > This patch adds APIs and a global notifier chain, a further > > > optimization might be per set notifier for ioasid_set aware users. > > > > > > Usage example: > > > KVM register notifier block such that it can keep its guest-host > > > PASID translation table in sync with any IOASID updates. > > > > > > VFIO publish IOASID change by performing alloc/free, bind/unbind > > > operations. > > > > > > IOMMU driver gets notified when IOASID is freed by VFIO or core mm > > > code such that PASID context can be cleaned up. > > > > above example looks mixed. You have KVM registers the notifier but > > finally having IOMMU driver to get notified... 😊 > > > Right, felt like a tale of two subscribers got mixed. I meant to list a > few use cases with publisher and subscriber roles separate. > I will change that to "Usage examples", and explicit state each role. > > > > > > > Signed-off-by: Liu Yi L <yi.l.liu@intel.com> > > > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com> > > > --- > > > drivers/iommu/ioasid.c | 61 > > > ++++++++++++++++++++++++++++++++++++++++++++++++++ > > > include/linux/ioasid.h | 40 +++++++++++++++++++++++++++++++++ > > > 2 files changed, 101 insertions(+) > > > > > > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c > > > index 8612fe6477dc..27dce2cb5af2 100644 > > > --- a/drivers/iommu/ioasid.c > > > +++ b/drivers/iommu/ioasid.c > > > @@ -11,6 +11,22 @@ > > > #include <linux/xarray.h> > > > > > > static DEFINE_XARRAY_ALLOC(ioasid_sets); > > > +/* > > > + * An IOASID could have multiple consumers. When a status change > > > occurs, > > > + * this notifier chain is used to keep them in sync. Each consumer > > > of the > > > + * IOASID service must register notifier block early to ensure no > > > events > > > + * are missed. > > > + * > > > + * 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 BLOCKING_NOTIFIER_HEAD(ioasid_chain); > > > + > > > /** > > > * struct ioasid_set_data - Meta data about ioasid_set > > > * > > > @@ -408,6 +424,7 @@ static void ioasid_free_locked(ioasid_t ioasid) > > > { > > > struct ioasid_data *ioasid_data; > > > struct ioasid_set_data *sdata; > > > + struct ioasid_nb_args args; > > > > > > ioasid_data = xa_load(&active_allocator->xa, ioasid); > > > if (!ioasid_data) { > > > @@ -415,6 +432,13 @@ static void ioasid_free_locked(ioasid_t ioasid) > > > return; > > > } > > > > > > + args.id = ioasid; > > > + args.sid = ioasid_data->sdata->sid; > > > + args.pdata = ioasid_data->private; > > > + args.set_token = ioasid_data->sdata->token; > > > + > > > + /* Notify all users that this IOASID is being freed */ > > > + blocking_notifier_call_chain(&ioasid_chain, IOASID_FREE, > > > &args); active_allocator->ops->free(ioasid, > > > active_allocator->ops->pdata); /* Custom allocator needs additional > > > steps to free the xa element */ if (active_allocator->flags & > > > IOASID_ALLOCATOR_CUSTOM) { @@ -624,6 +648,43 @@ int > > > ioasid_find_sid(ioasid_t ioasid) } > > > EXPORT_SYMBOL_GPL(ioasid_find_sid); > > > > > > +int ioasid_add_notifier(struct notifier_block *nb) > > > +{ > > > + return blocking_notifier_chain_register(&ioasid_chain, nb); > > > +} > > > +EXPORT_SYMBOL_GPL(ioasid_add_notifier); > > > + > > > +void ioasid_remove_notifier(struct notifier_block *nb) > > > +{ > > > + blocking_notifier_chain_unregister(&ioasid_chain, nb); > > > +} > > > +EXPORT_SYMBOL_GPL(ioasid_remove_notifier); > > > > register/unregister > > > Sounds good. > > > > + > > > +int ioasid_notify(ioasid_t ioasid, enum ioasid_notify_val cmd) > > > > add a comment on when this function should be used? > > > Sure, how about: > /** > * 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 > * > */
looks good.
> > > > +{ > > > + struct ioasid_data *ioasid_data; > > > + struct ioasid_nb_args args; > > > + int ret = 0; > > > + > > > + mutex_lock(&ioasid_allocator_lock); > > > + ioasid_data = xa_load(&active_allocator->xa, ioasid); > > > + if (!ioasid_data) { > > > + pr_err("Trying to free unknown IOASID %u\n", > > > ioasid); > > > > why is it fixed to 'free'? > > > Good catch, it shouldn;t be just free. It was a relic of early test > case. > > > > + mutex_unlock(&ioasid_allocator_lock); > > > + return -EINVAL; > > > + } > > > + > > > + args.id = ioasid; > > > + args.sid = ioasid_data->sdata->sid; > > > + args.pdata = ioasid_data->private; > > > > why no token info as did in ioasid_free? > > > Good catch, should include token as well. It is better to include all > the data such that subscribers don't have to do any lookup which may > cause race. > > > > + > > > + ret = blocking_notifier_call_chain(&ioasid_chain, cmd, > > > &args); > > > + mutex_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 e19c0ad93bd7..32d032913828 100644 > > > --- a/include/linux/ioasid.h > > > +++ b/include/linux/ioasid.h > > > @@ -4,6 +4,7 @@ > > > > > > #include <linux/types.h> > > > #include <linux/errno.h> > > > +#include <linux/notifier.h> > > > > > > #define INVALID_IOASID ((ioasid_t)-1) > > > #define INVALID_IOASID_SET (-1) > > > @@ -30,6 +31,27 @@ 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, > > > +}; > > > > Curious why IOASID_ALLOC is not notified aumatically within > > ioasid_alloc similar to ioasid_free, while leaving to the publisher? > > BIND/UNBIND is a publisher thing but a bit strange to see ALLOC/FREE > > with different policy here. > > > I don't see a use case for ALLOC notification yet. Any user does the > allocation would the be the first and only one know about this IOASID. > > Unless we have set level notifier, which may be interested in a new > IOASID being allocated within the set.
then remove this type until it is actually required when supporting set-level notifier?
> > > > + > > > +/** > > > + * struct ioasid_nb_args - Argument provided by IOASID core when > > > notifier > > > + * is called. > > > + * @id: the IOASID being notified > > > + * @sid: the IOASID set @id belongs to > > > + * @pdata: the private data attached to the IOASID > > > + */ > > > +struct ioasid_nb_args { > > > + ioasid_t id; > > > + int sid; > > > + struct ioasid_set *set_token; > > > + void *pdata; > > > +}; > > > /* Shared IOASID set for reserved for host system use */ > > > extern int system_ioasid_sid; > > > > > > @@ -43,11 +65,15 @@ void *ioasid_find(int sid, ioasid_t ioasid, bool > > > (*getter)(void *)); > > > int ioasid_register_allocator(struct ioasid_allocator_ops > > > *allocator); void ioasid_unregister_allocator(struct > > > ioasid_allocator_ops *allocator); int ioasid_attach_data(ioasid_t > > > ioasid, void *data); +int ioasid_add_notifier(struct notifier_block > > > *nb); +void ioasid_remove_notifier(struct notifier_block *nb); > > > void ioasid_install_capacity(ioasid_t total); > > > int ioasid_alloc_system_set(int quota); > > > int ioasid_alloc_set(struct ioasid_set *token, ioasid_t quota, int > > > *sid); void ioasid_free_set(int sid, bool destroy_set); > > > int ioasid_find_sid(ioasid_t ioasid); > > > +int ioasid_notify(ioasid_t id, enum ioasid_notify_val cmd); > > > + > > > #else /* !CONFIG_IOASID */ > > > static inline ioasid_t ioasid_alloc(int sid, ioasid_t min, > > > ioasid_t max, void *private) > > > @@ -73,6 +99,20 @@ static inline void *ioasid_find(int sid, > > > ioasid_t ioasid, bool (*getter)(void *) > > > return NULL; > > > } > > > > > > +static inline int ioasid_add_notifier(struct notifier_block *nb) > > > +{ > > > + return -ENOTSUPP; > > > +} > > > + > > > +static inline void ioasid_remove_notifier(struct notifier_block > > > *nb) +{ > > > +} > > > + > > > +int ioasid_notify(ioasid_t ioasid, enum ioasid_notify_val cmd) > > > +{ > > > + return -ENOTSUPP; > > > +} > > > + > > > static inline int ioasid_register_allocator(struct > > > ioasid_allocator_ops *allocator) > > > { > > > return -ENOTSUPP; > > > -- > > > 2.7.4 > > > > [Jacob Pan]
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