linux-kernel - Re: [PATCH 09/10] iommu/ioasid: Support ioasid

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Date:   Fri, 27 Mar 2020 16:30:57 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 09/10] iommu/ioasid: Support ioasid_set quota adjustment

On Fri, 27 Mar 2020 10:09:04 +0000
"Tian, Kevin" <kevin.tian@...el.com> wrote:

> > From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > 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.

> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > ---
> >  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]