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

["Tian, Kevin" <kevin.tian@intel.com>]

> 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?

> +{
> +	struct domain_capsule dc = {.data = data};
> +	struct vfio_domain *d;
> +	struct vfio_group *g;
> +	int ret = 0;
> +
> +	list_for_each_entry(d, &iommu->domain_list, next) {
> +		dc.domain = d->domain;
> +		list_for_each_entry(g, &d->group_list, next) {
> +			ret = iommu_group_for_each_dev(g-
> >iommu_group,
> +						       &dc, fn);
> +			if (ret)
> +				break;
> +		}
> +	}
> +	return ret;
> +}
> +
>  static int put_pfn(unsigned long pfn, int prot);
> 
>  /*
> @@ -2211,6 +2239,15 @@ static int vfio_iommu_iova_build_caps(struct
> vfio_iommu *iommu,
>  	return ret;
>  }
> 
> +static int vfio_cache_inv_fn(struct device *dev, void *data)
> +{
> +	struct domain_capsule *dc = (struct domain_capsule *)data;
> +	struct vfio_iommu_type1_cache_invalidate *ustruct =
> +		(struct vfio_iommu_type1_cache_invalidate *)dc->data;
> +
> +	return iommu_cache_invalidate(dc->domain, dev, &ustruct->info);
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>  				   unsigned int cmd, unsigned long arg)
>  {
> @@ -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.

> +		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...

> + */
> +struct vfio_iommu_type1_cache_invalidate {
> +	__u32   argsz;
> +	__u32   flags;
> +	struct iommu_cache_invalidate_info info;
> +};
> +#define VFIO_IOMMU_CACHE_INVALIDATE      _IO(VFIO_TYPE, VFIO_BASE
> + 24)
> +
>  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU --------
> */
> 
>  /*
> --
> 2.7.4

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