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

["Liu, Yi L" <yi.l.liu@intel.com>]

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?

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,
> > + *			struct vfio_iommu_type1_cache_invalidate)
> > + *
> > + * Propagate guest IOMMU cache invalidation to the host.
> 
> guest or first-level/stage-1? Ideally userspace application may also bind its own
> address space as stage-1 one day...

Should be first-level/stage-1. Will correct it.

Thanks,
Yi Liu

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