linux-kernel - Re: [PATCH v2 5/9] iommu/ioasid: Introduce ioasid_set private ID

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Message-ID: <bc955e7d-e9be-bae4-02fd-66bc81d26f39@redhat.com>
Date:   Thu, 10 Sep 2020 11:18:02 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     Jacob Pan <jacob.pan.linux@...il.com>,
        iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>, Wu Hao <hao.wu@...el.com>
Subject: Re: [PATCH v2 5/9] iommu/ioasid: Introduce ioasid_set private ID

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@...hat.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@...ux.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@...ts.linux-foundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> 
> [Jacob Pan]
> 

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