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SubjectRe: [PATCH v2 5/9] iommu/ioasid: Introduce ioasid_set private ID
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Hi Jacob,

On 9/9/20 12:40 AM, Jacob Pan wrote:
> On Tue, 1 Sep 2020 17:38:44 +0200
> Auger Eric <eric.auger@redhat.com> wrote:
>
>> Hi Jacob,
>> On 8/22/20 6:35 AM, 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.
>> I would remove "For IOASID that is already allocated, private ID
>> within the set can be attached via this API"
> I guess it is implied. Will remove.
>
>>> + */
>>> +int ioasid_attach_spid(ioasid_t ioasid, ioasid_t spid)
>>> +{
>>> + struct ioasid_data *ioasid_data;
>>> + int ret = 0;
>>> +
>>> + spin_lock(&ioasid_allocator_lock);
>> We keep on saying the SPID is local to an IOASID set but we don't
>> check any IOASID set contains this ioasid. It looks a bit weird to me.
> We store ioasid_set inside ioasid_data when an IOASID is allocated, so
> we don't need to search all the ioasid_sets. Perhaps I missed your
> point?
No I think it became clearer ;-)
>
>>> + 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;
>> is there any way/need to remove an spid binding?
> For guest SVA, we attach SPID as a guest PASID during bind guest page
> table. Unbind does the opposite, ioasid_attach_spid() with
> spid=INVALID_IOASID clears the binding.
>
> Perhaps add more symmetric functions? i.e.
> ioasid_detach_spid(ioasid_t ioasid)
> ioasid_attach_spid(struct ioasid_set *set, ioasid_t ioasid)
yep make sense

Thanks

Eric
>
>>> +
>>> +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)
>>> +{
>>> + 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);
>>> + 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;
>>> +}
>>> +
>>> #endif /* CONFIG_IOASID */
>>> #endif /* __LINUX_IOASID_H */
>>>
>> Thanks
>>
>> Eric
>>
>> _______________________________________________
>> iommu mailing list
>> iommu@lists.linux-foundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>
> [Jacob Pan]
>

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