RE: [PATCH v1 7/8] vfio/type1: Add VFIO_IOMMU_CACHE_INVALIDATE

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Sunday, March 22, 2020 8:32 PM
> 
> From: Liu Yi L <yi.l.liu@xxxxxxxxxxxxxxx>
> 
> For VFIO IOMMUs with the type VFIO_TYPE1_NESTING_IOMMU, guest
> "owns" the
> first-level/stage-1 translation structures, the host IOMMU driver has no
> knowledge of first-level/stage-1 structure cache updates unless the guest
> invalidation requests are trapped and propagated to the host.
> 
> This patch adds a new IOCTL VFIO_IOMMU_CACHE_INVALIDATE to
> propagate guest
> first-level/stage-1 IOMMU cache invalidations to host to ensure IOMMU
> cache
> correctness.
> 
> With this patch, vSVA (Virtual Shared Virtual Addressing) can be used safely
> as the host IOMMU iotlb correctness are ensured.
> 
> Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> CC: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Cc: Eric Auger <eric.auger@xxxxxxxxxx>
> Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxxxxxxxx>
> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 49
> +++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       | 22 ++++++++++++++++++
>  2 files changed, 71 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c
> b/drivers/vfio/vfio_iommu_type1.c
> index a877747..937ec3f 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -2423,6 +2423,15 @@ static long
> vfio_iommu_type1_unbind_gpasid(struct vfio_iommu *iommu,
>  	return ret;
>  }
> 
> +static int vfio_cache_inv_fn(struct device *dev, void *data)

vfio_iommu_cache_inv_fn

> +{
> +	struct domain_capsule *dc = (struct domain_capsule *)data;
> +	struct iommu_cache_invalidate_info *cache_inv_info =
> +		(struct iommu_cache_invalidate_info *) dc->data;
> +
> +	return iommu_cache_invalidate(dc->domain, dev, cache_inv_info);
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>  				   unsigned int cmd, unsigned long arg)
>  {
> @@ -2629,6 +2638,46 @@ static long vfio_iommu_type1_ioctl(void
> *iommu_data,
>  		}
>  		kfree(gbind_data);
>  		return ret;
> +	} else if (cmd == VFIO_IOMMU_CACHE_INVALIDATE) {
> +		struct vfio_iommu_type1_cache_invalidate cache_inv;
> +		u32 version;
> +		int info_size;
> +		void *cache_info;
> +		int ret;
> +
> +		minsz = offsetofend(struct
> vfio_iommu_type1_cache_invalidate,
> +				    flags);
> +
> +		if (copy_from_user(&cache_inv, (void __user *)arg, minsz))
> +			return -EFAULT;
> +
> +		if (cache_inv.argsz < minsz || cache_inv.flags)
> +			return -EINVAL;
> +
> +		/* Get the version of struct iommu_cache_invalidate_info */
> +		if (copy_from_user(&version,
> +			(void __user *) (arg + minsz), sizeof(version)))
> +			return -EFAULT;
> +
> +		info_size = iommu_uapi_get_data_size(
> +					IOMMU_UAPI_CACHE_INVAL,
> version);
> +
> +		cache_info = kzalloc(info_size, GFP_KERNEL);
> +		if (!cache_info)
> +			return -ENOMEM;
> +
> +		if (copy_from_user(cache_info,
> +			(void __user *) (arg + minsz), info_size)) {
> +			kfree(cache_info);
> +			return -EFAULT;
> +		}
> +
> +		mutex_lock(&iommu->lock);
> +		ret = vfio_iommu_for_each_dev(iommu, vfio_cache_inv_fn,
> +					    cache_info);
> +		mutex_unlock(&iommu->lock);
> +		kfree(cache_info);
> +		return ret;
>  	}
> 
>  	return -ENOTTY;
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 2235bc6..62ca791 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -899,6 +899,28 @@ struct vfio_iommu_type1_bind {
>   */
>  #define VFIO_IOMMU_BIND		_IO(VFIO_TYPE, VFIO_BASE + 23)
> 
> +/**
> + * VFIO_IOMMU_CACHE_INVALIDATE - _IOW(VFIO_TYPE, VFIO_BASE + 24,
> + *			struct vfio_iommu_type1_cache_invalidate)
> + *
> + * Propagate guest IOMMU cache invalidation to the host. The cache
> + * invalidation information is conveyed by @cache_info, the content
> + * format would be structures defined in uapi/linux/iommu.h. User
> + * should be aware of that the struct  iommu_cache_invalidate_info
> + * has a @version field, vfio needs to parse this field before getting
> + * data from userspace.
> + *
> + * Availability of this IOCTL is after VFIO_SET_IOMMU.
> + *
> + * returns: 0 on success, -errno on failure.
> + */
> +struct vfio_iommu_type1_cache_invalidate {
> +	__u32   argsz;
> +	__u32   flags;
> +	struct	iommu_cache_invalidate_info cache_info;
> +};
> +#define VFIO_IOMMU_CACHE_INVALIDATE      _IO(VFIO_TYPE, VFIO_BASE +
> 24)
> +
>  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
> 
>  /*
> --
> 2.7.4

This patch looks good to me in general. But since there is still
a major open about version compatibility, I'll hold my r-b until
that open is closed. ð

Thanks
Kevin