Re: [RFC v2 1/3] vfio: VFIO_IOMMU_CACHE_INVALIDATE

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 25 Oct 2019 11:20:40 +0000
"Liu, Yi L" <yi.l.liu@intel.com> wrote:

> Hi Kevin,
> 
> > From: Tian, Kevin
> > Sent: Friday, October 25, 2019 5:14 PM
> > To: Liu, Yi L <yi.l.liu@intel.com>; alex.williamson@redhat.com;
> > Subject: RE: [RFC v2 1/3] vfio: VFIO_IOMMU_CACHE_INVALIDATE
> >   
> > > From: Liu, Yi L
> > > Sent: Thursday, October 24, 2019 8:26 PM
> > >
> > > From: Liu Yi L <yi.l.liu@linux.intel.com>
> > >
> > > When the guest "owns" the stage 1 translation structures,  the host
> > > IOMMU driver has no knowledge of caching structure updates unless the
> > > guest invalidation requests are trapped and passed down to the host.
> > >
> > > This patch adds the VFIO_IOMMU_CACHE_INVALIDATE ioctl with aims at
> > > propagating guest stage1 IOMMU cache invalidations to the host.
> > >
> > > Cc: Kevin Tian <kevin.tian@intel.com>
> > > Signed-off-by: Liu Yi L <yi.l.liu@linux.intel.com>
> > > Signed-off-by: Eric Auger <eric.auger@redhat.com>
> > > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > > ---
> > >  drivers/vfio/vfio_iommu_type1.c | 55
> > > +++++++++++++++++++++++++++++++++++++++++
> > >  include/uapi/linux/vfio.h       | 13 ++++++++++
> > >  2 files changed, 68 insertions(+)
> > >
> > > diff --git a/drivers/vfio/vfio_iommu_type1.c
> > > b/drivers/vfio/vfio_iommu_type1.c index 96fddc1d..cd8d3a5 100644
> > > --- a/drivers/vfio/vfio_iommu_type1.c
> > > +++ b/drivers/vfio/vfio_iommu_type1.c
> > > @@ -124,6 +124,34 @@ struct vfio_regions {
> > >  #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)	\
> > >  					(!list_empty(&iommu->domain_list))
> > >
> > > +struct domain_capsule {
> > > +	struct iommu_domain *domain;
> > > +	void *data;
> > > +};
> > > +
> > > +/* iommu->lock must be held */
> > > +static int
> > > +vfio_iommu_lookup_dev(struct vfio_iommu *iommu,
> > > +		      int (*fn)(struct device *dev, void *data),
> > > +		      void *data)  
> > 
> > 'lookup' usually means find a device and then return. But the real purpose here is to
> > loop all the devices within this container and then do something. Does it make more
> > sense to be vfio_iommu_for_each_dev?  

+1
 
> yep, I can replace it.
> 
> >   
> > > +{
> > > +	struct domain_capsule dc = {.data = data};
> > > +	struct vfio_domain *d;  
> [...]
> > 2315,6 +2352,24 @@  
> > > static long vfio_iommu_type1_ioctl(void *iommu_data,
> > >
> > >  		return copy_to_user((void __user *)arg, &unmap, minsz) ?
> > >  			-EFAULT : 0;
> > > +	} else if (cmd == VFIO_IOMMU_CACHE_INVALIDATE) {
> > > +		struct vfio_iommu_type1_cache_invalidate ustruct;  
> > 
> > it's weird to call a variable as struct.  
> 
> Will fix it.
> 
> > > +		int ret;
> > > +
> > > +		minsz = offsetofend(struct
> > > vfio_iommu_type1_cache_invalidate,
> > > +				    info);
> > > +
> > > +		if (copy_from_user(&ustruct, (void __user *)arg, minsz))
> > > +			return -EFAULT;
> > > +
> > > +		if (ustruct.argsz < minsz || ustruct.flags)
> > > +			return -EINVAL;
> > > +
> > > +		mutex_lock(&iommu->lock);
> > > +		ret = vfio_iommu_lookup_dev(iommu, vfio_cache_inv_fn,
> > > +					    &ustruct);
> > > +		mutex_unlock(&iommu->lock);
> > > +		return ret;
> > >  	}
> > >
> > >  	return -ENOTTY;
> > > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > > index 9e843a1..ccf60a2 100644
> > > --- a/include/uapi/linux/vfio.h
> > > +++ b/include/uapi/linux/vfio.h
> > > @@ -794,6 +794,19 @@ struct vfio_iommu_type1_dma_unmap {
> > >  #define VFIO_IOMMU_ENABLE	_IO(VFIO_TYPE, VFIO_BASE + 15)
> > >  #define VFIO_IOMMU_DISABLE	_IO(VFIO_TYPE, VFIO_BASE + 16)
> > >
> > > +/**
> > > + * VFIO_IOMMU_CACHE_INVALIDATE - _IOWR(VFIO_TYPE, VFIO_BASE +
> > > 24,

What's going on with these ioctl numbers?  AFAICT[1] we've used up
through VFIO_BASE + 21, this jumps to 24, the next patch skips to 27,
then the last patch fills in 28 & 29.  Thanks,

Alex

[1] git grep -h VFIO_BASE | grep "VFIO_BASE +" | grep -e ^#define | \
    awk '{print $NF}' | tr -d ')' | sort -u -n