RE: [PATCH 09/10] iommu/ioasid: Support ioasid_set quota adjustment

[Tian, Kevin]

> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Sent: Saturday, March 28, 2020 7:31 AM
> 
> On Fri, 27 Mar 2020 10:09:04 +0000
> "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:
> 
> > > From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > > Sent: Thursday, March 26, 2020 1:56 AM
> > >
> > > IOASID set is allocated with an initial quota, at runtime there may
> > > be needs to balance IOASID resources among different VMs/sets.
> > >
> >
> > I may overlook previous patches but I didn't see any place setting the
> > initial quota...
> >
> Initial quota is in place when the ioasid_set is allocated.
> 
> > > This patch adds a new API to adjust per set quota.
> >
> > since this is purely an internal kernel API, implies that the
> > publisher (e.g. VFIO) is responsible for exposing its own uAPI to set
> > the quota?
> >
> yes, VFIO will do the adjustment. I think Alex suggested module
> parameters.

ok, I remember that.

> 
> > >
> > > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > > ---
> > >  drivers/iommu/ioasid.c | 44
> > > ++++++++++++++++++++++++++++++++++++++++++++
> > >  include/linux/ioasid.h |  6 ++++++
> > >  2 files changed, 50 insertions(+)
> > >
> > > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> > > index 27dce2cb5af2..5ac28862a1db 100644
> > > --- a/drivers/iommu/ioasid.c
> > > +++ b/drivers/iommu/ioasid.c
> > > @@ -578,6 +578,50 @@ void ioasid_free_set(int sid, bool destroy_set)
> > >  }
> > >  EXPORT_SYMBOL_GPL(ioasid_free_set);
> > >
> > > +/**
> > > + * ioasid_adjust_set - Adjust the quota of an IOASID set
> > > + * @quota:	Quota allowed in this set
> > > + * @sid:	IOASID set ID to be assigned
> > > + *
> > > + * Return 0 on success. If the new quota is smaller than the
> > > number of
> > > + * IOASIDs already allocated, -EINVAL will be returned. No change
> > > will be
> > > + * made to the existing quota.
> > > + */
> > > +int ioasid_adjust_set(int sid, int quota)
> > > +{
> > > +	struct ioasid_set_data *sdata;
> > > +	int ret = 0;
> > > +
> > > +	mutex_lock(&ioasid_allocator_lock);
> > > +	sdata = xa_load(&ioasid_sets, sid);
> > > +	if (!sdata || sdata->nr_ioasids > quota) {
> > > +		pr_err("Failed to adjust IOASID set %d quota %d\n",
> > > +			sid, quota);
> > > +		ret = -EINVAL;
> > > +		goto done_unlock;
> > > +	}
> > > +
> > > +	if (quota >= ioasid_capacity_avail) {
> > > +		ret = -ENOSPC;
> > > +		goto done_unlock;
> > > +	}
> > > +
> > > +	/* Return the delta back to system pool */
> > > +	ioasid_capacity_avail += sdata->size - quota;
> > > +
> > > +	/*
> > > +	 * May have a policy to prevent giving all available
> > > IOASIDs
> > > +	 * to one set. But we don't enforce here, it should be in
> > > the
> > > +	 * upper layers.
> > > +	 */
> > > +	sdata->size = quota;
> > > +
> > > +done_unlock:
> > > +	mutex_unlock(&ioasid_allocator_lock);
> > > +
> > > +	return ret;
> > > +}
> > > +EXPORT_SYMBOL_GPL(ioasid_adjust_set);
> > >
> > >  /**
> > >   * ioasid_find - Find IOASID data
> > > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
> > > index 32d032913828..6e7de6fb91bf 100644
> > > --- a/include/linux/ioasid.h
> > > +++ b/include/linux/ioasid.h
> > > @@ -73,6 +73,7 @@ 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);
> > > +int ioasid_adjust_set(int sid, int quota);
> > >
> > >  #else /* !CONFIG_IOASID */
> > >  static inline ioasid_t ioasid_alloc(int sid, ioasid_t min,
> > > @@ -136,5 +137,10 @@ static inline int ioasid_alloc_system_set(int
> > > quota) return -ENOTSUPP;
> > >  }
> > >
> > > +static inline int ioasid_adjust_set(int sid, int quota)
> > > +{
> > > +	return -ENOTSUPP;
> > > +}
> > > +
> > >  #endif /* CONFIG_IOASID */
> > >  #endif /* __LINUX_IOASID_H */
> > > --
> > > 2.7.4
> >
> 
> [Jacob Pan]