linux-kernel - Re: [RFC][PATCH 2/3] iommu/fsl: Add iommu domain attributes required by fsl PAMU driver.

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Date:	Wed, 19 Sep 2012 19:12:16 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Kumar Gala <galak@...nel.crashing.org>
CC:	"<b16395@...escale.com>" <b16395@...escale.com>,
	<joerg.roedel@....com>, <iommu@...ts.linux-foundation.org>,
	<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	Varun Sethi <Varun.Sethi@...escale.com>
Subject: Re: [RFC][PATCH 2/3] iommu/fsl: Add iommu domain attributes
 required by fsl PAMU driver.

On 09/19/2012 08:52:27 AM, Kumar Gala wrote:
> 
> On Sep 19, 2012, at 8:17 AM, <b16395@...escale.com>  
> <b16395@...escale.com> wrote:
> 
> > From: Varun Sethi <Varun.Sethi@...escale.com>
> >
> > Added the following domain attributes required by FSL PAMU driver:
> > 1. Subwindows field added to the iommu domain geometry attribute.
> > 2. Added new iommu stash attribute, which allows setting of the
> >   LIODN specific stash id parameter through IOMMU API.
> > 3. Added an attribute for enabling/disabling DMA to a particular
> >   memory window.
> >
> > Signed-off-by: Varun Sethi <Varun.Sethi@...escale.com>
> > ---
> > include/linux/iommu.h |   30 ++++++++++++++++++++++++++++++
> > 1 files changed, 30 insertions(+), 0 deletions(-)
> >
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index 7e83370..eaa40c6 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -44,6 +44,28 @@ struct iommu_domain_geometry {
> > 	dma_addr_t aperture_start; /* First address that can be  
> mapped    */
> > 	dma_addr_t aperture_end;   /* Last address that can be  
> mapped     */
> > 	bool force_aperture;       /* DMA only allowed in mappable  
> range? */
> > +
> > +	/* The subwindows field indicates number of DMA subwindows  
> supported
> > +	 * by the geometry. Following is the interpretation of
> > +	 * values for this field:
> > +	 * 0 : This implies that the supported geometry size is 1 MB
> > +         * with each subwindow size being 4KB. Thus number of  
> subwindows
> > +	 * being = 1MB/4KB = 256.
> > +	 * 1 : Only one DMA window i.e. no subwindows.
> > +	 * value other than 0 or 1 would indicate actual number of  
> subwindows.
> > +	 */
> > +	u32 subwindows;
> > +};
> > +
> > +/* This attribute corresponds to IOMMUs capable of generating
> > + * a stash transaction. A stash transaction is typically a
> > + * hardware initiated prefetch of data from memory to cache.
> > + * This attribute allows configuring stashig specific parameters
> > + * in the IOMMU hardware.
> > + */
> > +struct iommu_stash_attribute {
> > +	u32 	cpu;	/* cpu number */
> > +	u32 	cache;	/* cache to stash to: L1,L2,L3 */
> 
> seems like this should be enum instead of u32 for cache
> 
> With enum being something like:
> 
> enum iommu_attr_stash_cache {
> 	IOMMU_ATTR_CACHE_L1,
> 	IOMMU_ATTR_CACHE_L2,
> 	IOMMU_ATTR_CACHE_L3,
> };

Don't we want these structs to be usable via some VFIO ioctl?  In that  
case they need to use fixed size types.

-Scott
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