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SubjectRe: [PATCH v2 5/9] iommu/ioasid: Introduce ioasid_set private ID
On Tue, 25 Aug 2020 12:22:09 +0200
Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:

> On Fri, Aug 21, 2020 at 09:35:14PM -0700, Jacob Pan wrote:
> > When an IOASID set is used for guest SVA, each VM will acquire its
> > ioasid_set for IOASID allocations. IOASIDs within the VM must have a
> > host/physical IOASID backing, mapping between guest and host IOASIDs can
> > be non-identical. IOASID set private ID (SPID) is introduced in this
> > patch to be used as guest IOASID. However, the concept of ioasid_set
> > specific namespace is generic, thus named SPID.
> >
> > As SPID namespace is within the IOASID set, the IOASID core can provide
> > lookup services at both directions. SPIDs may not be allocated when its
> > IOASID is allocated, the mapping between SPID and IOASID is usually
> > established when a guest page table is bound to a host PASID.
> >
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> > drivers/iommu/ioasid.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/ioasid.h | 12 +++++++++++
> > 2 files changed, 66 insertions(+)
> >
> > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> > index 5f31d63c75b1..c0aef38a4fde 100644
> > --- a/drivers/iommu/ioasid.c
> > +++ b/drivers/iommu/ioasid.c
> > @@ -21,6 +21,7 @@ enum ioasid_state {
> > * struct ioasid_data - Meta data about ioasid
> > *
> > * @id: Unique ID
> > + * @spid: Private ID unique within a set
> > * @users Number of active users
> > * @state Track state of the IOASID
> > * @set Meta data of the set this IOASID belongs to
> > @@ -29,6 +30,7 @@ enum ioasid_state {
> > */
> > struct ioasid_data {
> > ioasid_t id;
> > + ioasid_t spid;
> > struct ioasid_set *set;
> > refcount_t users;
> > enum ioasid_state state;
> > @@ -326,6 +328,58 @@ int ioasid_attach_data(ioasid_t ioasid, void *data)
> > EXPORT_SYMBOL_GPL(ioasid_attach_data);
> >
> > /**
> > + * ioasid_attach_spid - Attach ioasid_set private ID to an IOASID
> > + *
> > + * @ioasid: the ID to attach
> > + * @spid: the ioasid_set private ID of @ioasid
> > + *
> > + * For IOASID that is already allocated, private ID within the set can be
> > + * attached via this API. Future lookup can be done via ioasid_find.
>
> via ioasid_find_by_spid()?
>
yes, will update.

> > + */
> > +int ioasid_attach_spid(ioasid_t ioasid, ioasid_t spid)
> > +{
> > + struct ioasid_data *ioasid_data;
> > + int ret = 0;
> > +
> > + spin_lock(&ioasid_allocator_lock);
> > + ioasid_data = xa_load(&active_allocator->xa, ioasid);
> > +
> > + if (!ioasid_data) {
> > + pr_err("No IOASID entry %d to attach SPID %d\n",
> > + ioasid, spid);
> > + ret = -ENOENT;
> > + goto done_unlock;
> > + }
> > + ioasid_data->spid = spid;
> > +
> > +done_unlock:
> > + spin_unlock(&ioasid_allocator_lock);
> > + return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_attach_spid);
> > +
> > +ioasid_t ioasid_find_by_spid(struct ioasid_set *set, ioasid_t spid)
>
> Maybe add a bit of documentation as this is public-facing.
>
Good point, I will add
/**
* ioasid_find_by_spid - Find the system-wide IOASID by a set private ID and
* its set.
*
* @set: the ioasid_set to search within
* @spid: the set private ID
*
* Given a set private ID and its IOASID set, find the system-wide IOASID. Take
* a reference upon finding the matching IOASID. Return INVALID_IOASID if the
* IOASID is not found in the set or the set is not valid.
*/

> > +{
> > + struct ioasid_data *entry;
> > + unsigned long index;
> > +
> > + if (!xa_load(&ioasid_sets, set->sid)) {
> > + pr_warn("Invalid set\n");
> > + return INVALID_IOASID;
> > + }
> > +
> > + xa_for_each(&set->xa, index, entry) {
> > + if (spid == entry->spid) {
> > + pr_debug("Found ioasid %lu by spid %u\n", index, spid);
> > + refcount_inc(&entry->users);
>
> Nothing prevents ioasid_free() from concurrently dropping the refcount to
> zero and calling ioasid_do_free(). The caller will later call ioasid_put()
> on a stale/reallocated index.
>
right, need to add spin_lock(&ioasid_allocator_lock);

> > + return index;
> > + }
> > + }
> > + return INVALID_IOASID;
> > +}
> > +EXPORT_SYMBOL_GPL(ioasid_find_by_spid);
> > +
> > +/**
> > * ioasid_alloc - Allocate an IOASID
> > * @set: the IOASID set
> > * @min: the minimum ID (inclusive)
> > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
> > index 310abe4187a3..d4b3e83672f6 100644
> > --- a/include/linux/ioasid.h
> > +++ b/include/linux/ioasid.h
> > @@ -73,6 +73,8 @@ bool ioasid_is_active(ioasid_t ioasid);
> >
> > 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_allocator(struct ioasid_allocator_ops *allocator);
> > void ioasid_unregister_allocator(struct ioasid_allocator_ops *allocator);
> > void ioasid_is_in_set(struct ioasid_set *set, ioasid_t ioasid);
> > @@ -136,5 +138,15 @@ static inline int ioasid_attach_data(ioasid_t ioasid, void *data)
> > return -ENOTSUPP;
> > }
> >
> > +staic inline int ioasid_attach_spid(ioasid_t ioasid, ioasid_t spid)
> > +{
> > + return -ENOTSUPP;
> > +}
> > +
> > +static inline ioasid_t ioasid_find_by_spid(struct ioasid_set *set, ioasid_t spid)
> > +{
> > + return -ENOTSUPP;
>
> INVALID_IOASID
>
right, will fix.

Thanks!

> Thanks,
> Jean
>
> > +}
> > +
> > #endif /* CONFIG_IOASID */
> > #endif /* __LINUX_IOASID_H */
> > --
> > 2.7.4
> >
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

[Jacob Pan]

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