Re: [RFC v3 04/21] vfio: VFIO_IOMMU_SET_PASID_TABLE

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

On Tue,  8 Jan 2019 11:26:16 +0100
Eric Auger <eric.auger@redhat.com> wrote:

> From: "Liu, Yi L" <yi.l.liu@linux.intel.com>
> 
> This patch adds VFIO_IOMMU_SET_PASID_TABLE ioctl which aims at
> passing the virtual iommu guest configuration to the VFIO driver
> downto to the iommu subsystem.
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Liu, Yi L <yi.l.liu@linux.intel.com>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> ---
> v2 -> v3:
> - s/BIND_PASID_TABLE/SET_PASID_TABLE
> 
> v1 -> v2:
> - s/BIND_GUEST_STAGE/BIND_PASID_TABLE
> - remove the struct device arg
> ---
>  drivers/vfio/vfio_iommu_type1.c | 31 +++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       |  8 ++++++++
>  2 files changed, 39 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 7651cfb14836..d9dd23f64f00 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -1644,6 +1644,24 @@ static int vfio_domains_have_iommu_cache(struct vfio_iommu *iommu)
>  	return ret;
>  }
>  
> +static int
> +vfio_set_pasid_table(struct vfio_iommu *iommu,
> +		      struct vfio_iommu_type1_set_pasid_table *ustruct)
> +{
> +	struct vfio_domain *d;
> +	int ret = 0;
> +
> +	mutex_lock(&iommu->lock);
> +
> +	list_for_each_entry(d, &iommu->domain_list, next) {
> +		ret = iommu_set_pasid_table(d->domain, &ustruct->config);
> +		if (ret)
> +			break;
> +	}

There's no unwind on failure here, leaves us in an inconsistent state
should something go wrong or domains don't have homogeneous PASID
support.  What's expected to happen if a PASID table is already set for
a domain, does it replace the old one or return -EBUSY?

> +	mutex_unlock(&iommu->lock);
> +	return ret;
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>  				   unsigned int cmd, unsigned long arg)
>  {
> @@ -1714,6 +1732,19 @@ 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_SET_PASID_TABLE) {
> +		struct vfio_iommu_type1_set_pasid_table ustruct;
> +
> +		minsz = offsetofend(struct vfio_iommu_type1_set_pasid_table,
> +				    config);
> +
> +		if (copy_from_user(&ustruct, (void __user *)arg, minsz))
> +			return -EFAULT;
> +
> +		if (ustruct.argsz < minsz || ustruct.flags)
> +			return -EINVAL;
> +
> +		return vfio_set_pasid_table(iommu, &ustruct);
>  	}
>  
>  	return -ENOTTY;
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 02bb7ad6e986..0d9f4090c95d 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -14,6 +14,7 @@
>  
>  #include <linux/types.h>
>  #include <linux/ioctl.h>
> +#include <linux/iommu.h>
>  
>  #define VFIO_API_VERSION	0
>  
> @@ -759,6 +760,13 @@ 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)
>  
> +struct vfio_iommu_type1_set_pasid_table {
> +	__u32	argsz;
> +	__u32	flags;
> +	struct iommu_pasid_table_config config;
> +};
> +#define VFIO_IOMMU_SET_PASID_TABLE	_IO(VFIO_TYPE, VFIO_BASE + 22)

-ENOCOMMENTS  Thanks,

Alex

> +
>  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
>  
>  /*