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

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Message-ID: <20200908154028.0ec5abba@jacob-builder>
Date:   Tue, 8 Sep 2020 15:40:28 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Auger Eric <eric.auger@...hat.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>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v2 5/9] iommu/ioasid: Introduce ioasid_set private ID

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?

> > +	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)

> > +
> > +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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