Re: [PATCH v11 01/13] vfio: VFIO_IOMMU_SET_PASID_TABLE

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

On Mon, 16 Nov 2020 12:00:18 +0100
Eric Auger <eric.auger@redhat.com> wrote:

> From: "Liu, Yi L" <yi.l.liu@linux.intel.com>
> 
> This patch adds an VFIO_IOMMU_SET_PASID_TABLE ioctl
> which aims to pass the virtual iommu guest configuration
> to the host. This latter takes the form of the so-called
> PASID table.
> 
> 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>
> 
> ---
> v11 -> v12:
> - use iommu_uapi_set_pasid_table
> - check SET and UNSET are not set simultaneously (Zenghui)
> 
> v8 -> v9:
> - Merge VFIO_IOMMU_ATTACH/DETACH_PASID_TABLE into a single
>   VFIO_IOMMU_SET_PASID_TABLE ioctl.
> 
> v6 -> v7:
> - add a comment related to VFIO_IOMMU_DETACH_PASID_TABLE
> 
> v3 -> v4:
> - restore ATTACH/DETACH
> - add unwind on failure
> 
> 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 | 65 +++++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       | 19 ++++++++++
>  2 files changed, 84 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 67e827638995..87ddd9e882dc 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -2587,6 +2587,41 @@ static int vfio_iommu_iova_build_caps(struct vfio_iommu *iommu,
>  	return ret;
>  }
>  
> +static void
> +vfio_detach_pasid_table(struct vfio_iommu *iommu)
> +{
> +	struct vfio_domain *d;
> +
> +	mutex_lock(&iommu->lock);
> +	list_for_each_entry(d, &iommu->domain_list, next)
> +		iommu_detach_pasid_table(d->domain);
> +
> +	mutex_unlock(&iommu->lock);
> +}
> +
> +static int
> +vfio_attach_pasid_table(struct vfio_iommu *iommu, unsigned long arg)
> +{
> +	struct vfio_domain *d;
> +	int ret = 0;
> +
> +	mutex_lock(&iommu->lock);
> +
> +	list_for_each_entry(d, &iommu->domain_list, next) {
> +		ret = iommu_uapi_attach_pasid_table(d->domain, (void __user *)arg);
> +		if (ret)
> +			goto unwind;
> +	}
> +	goto unlock;
> +unwind:
> +	list_for_each_entry_continue_reverse(d, &iommu->domain_list, next) {
> +		iommu_detach_pasid_table(d->domain);
> +	}
> +unlock:

This goto leap frog could be avoided with just:

list_for_each_entry(d, &iommu->domain_list, next) {
	ret = iommu_uapi_attach_pasid_table(d->domain, (void __user *)arg);
	if (ret) {
		list_for_each_entry_continue_reverse(d, &iommu->domain_list, next) {
			iommu_detach_pasid_table(d->domain);
		}
		break;
	}
}

> +	mutex_unlock(&iommu->lock);
> +	return ret;
> +}
> +
>  static int vfio_iommu_migration_build_caps(struct vfio_iommu *iommu,
>  					   struct vfio_info_cap *caps)
>  {
> @@ -2747,6 +2782,34 @@ static int vfio_iommu_type1_unmap_dma(struct vfio_iommu *iommu,
>  			-EFAULT : 0;
>  }
>  
> +static int vfio_iommu_type1_set_pasid_table(struct vfio_iommu *iommu,
> +					    unsigned long arg)
> +{
> +	struct vfio_iommu_type1_set_pasid_table spt;
> +	unsigned long minsz;
> +	int ret = -EINVAL;
> +
> +	minsz = offsetofend(struct vfio_iommu_type1_set_pasid_table, flags);
> +
> +	if (copy_from_user(&spt, (void __user *)arg, minsz))
> +		return -EFAULT;
> +
> +	if (spt.argsz < minsz)
> +		return -EINVAL;
> +
> +	if (spt.flags & VFIO_PASID_TABLE_FLAG_SET &&
> +	    spt.flags & VFIO_PASID_TABLE_FLAG_UNSET)
> +		return -EINVAL;
> +
> +	if (spt.flags & VFIO_PASID_TABLE_FLAG_SET)
> +		ret = vfio_attach_pasid_table(iommu, arg + minsz);
> +	else if (spt.flags & VFIO_PASID_TABLE_FLAG_UNSET) {
> +		vfio_detach_pasid_table(iommu);
> +		ret = 0;
> +	}

This doesn't really validate that the other flag bits are zero, ex.
user could pass flags = (1 << 8) | VFIO_PASID_TABLE_FLAG_SET and we'd
just ignore the extra bit.  So this probably needs to be:

if (spt.flags == VFIO_PASID_TABLE_FLAG_SET)
	ret = vfio_attach_pasid_table(iommu, arg + minsz);
else if (spt.flags == VFIO_PASID_TABLE_FLAG_UNSET)
	vfio_detach_pasid_table(iommu);

Or otherwise validate that none of the other bits are set.  It also
seems cleaner to me to set the initial value of ret = 0 and end this
with:

else
	ret = -EINVAL;


> +	return ret;
> +}
> +
>  static int vfio_iommu_type1_dirty_pages(struct vfio_iommu *iommu,
>  					unsigned long arg)
>  {
> @@ -2867,6 +2930,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  		return vfio_iommu_type1_unmap_dma(iommu, arg);
>  	case VFIO_IOMMU_DIRTY_PAGES:
>  		return vfio_iommu_type1_dirty_pages(iommu, arg);
> +	case VFIO_IOMMU_SET_PASID_TABLE:
> +		return vfio_iommu_type1_set_pasid_table(iommu, arg);
>  	default:
>  		return -ENOTTY;
>  	}
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 2f313a238a8f..78ce3ce6c331 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
>  
> @@ -1180,6 +1181,24 @@ struct vfio_iommu_type1_dirty_bitmap_get {
>  
>  #define VFIO_IOMMU_DIRTY_PAGES             _IO(VFIO_TYPE, VFIO_BASE + 17)
>  
> +/*
> + * VFIO_IOMMU_SET_PASID_TABLE - _IOWR(VFIO_TYPE, VFIO_BASE + 22,

We already reuse ioctl indexes between type1 and spapr (ex. +17 is
either VFIO_IOMMU_DIRTY_PAGES or VFIO_IOMMU_SPAPR_REGISTER_MEMORY
depending on the iommu type).  I wonder if we should reuse +18 here
instead.

> + *			struct vfio_iommu_type1_set_pasid_table)
> + *
> + * The SET operation passes a PASID table to the host while the
> + * UNSET operation detaches the one currently programmed. Setting
> + * a table while another is already programmed replaces the old table.
> + */
> +struct vfio_iommu_type1_set_pasid_table {
> +	__u32	argsz;
> +	__u32	flags;
> +#define VFIO_PASID_TABLE_FLAG_SET	(1 << 0)
> +#define VFIO_PASID_TABLE_FLAG_UNSET	(1 << 1)
> +	struct iommu_pasid_table_config config; /* used on SET */
> +};
> +
> +#define VFIO_IOMMU_SET_PASID_TABLE	_IO(VFIO_TYPE, VFIO_BASE + 22)
> +
>  /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
>  
>  /*