On Wed, 2015-09-30 at 20:26 +0530, Bharat Bhushan wrote:
> This patch allows the user-space to know whether msi-pages
> are automatically mapped with some magic iova or not.
> 
> Even if the msi-pages are automatically mapped, still user-space
> wants to over-ride the automatic iova selection for msi-mapping.
> For this user-space need to know whether it is allowed to change
> the automatic mapping or not and this API provides this mechanism.
> Follow up patches will provide how to over-ride this.
> 
> Signed-off-by: Bharat Bhushan <bharat.bhus...@freescale.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 32 ++++++++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       |  3 +++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index fa5d3e4..3315fb6 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -59,6 +59,7 @@ struct vfio_iommu {
>       struct rb_root          dma_list;
>       bool                    v2;
>       bool                    nesting;
> +     bool                    allow_msi_reconfig;
>       struct list_head        reserved_iova_list;
>  };
>  
> @@ -1117,6 +1118,23 @@ static int vfio_domains_have_iommu_cache(struct 
> vfio_iommu *iommu)
>       return ret;
>  }
>  
> +static
> +int vfio_domains_get_msi_maps(struct vfio_iommu *iommu,
> +                           struct iommu_domain_msi_maps *msi_maps)
> +{
> +     struct vfio_domain *d;
> +     int ret;
> +
> +     mutex_lock(&iommu->lock);
> +     /* All domains have same msi-automap property, pick first */
> +     d = list_first_entry(&iommu->domain_list, struct vfio_domain, next);
> +     ret = iommu_domain_get_attr(d->domain, DOMAIN_ATTR_MSI_MAPPING,
> +                                 msi_maps);
> +     mutex_unlock(&iommu->lock);
> +
> +     return ret;
> +}
> +
>  static long vfio_iommu_type1_ioctl(void *iommu_data,
>                                  unsigned int cmd, unsigned long arg)
>  {
> @@ -1138,6 +1156,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>               }
>       } else if (cmd == VFIO_IOMMU_GET_INFO) {
>               struct vfio_iommu_type1_info info;
> +             struct iommu_domain_msi_maps msi_maps;
> +             int ret;
>  
>               minsz = offsetofend(struct vfio_iommu_type1_info, iova_pgsizes);
>  
> @@ -1149,6 +1169,18 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  
>               info.flags = 0;
>  
> +             ret = vfio_domains_get_msi_maps(iommu, &msi_maps);
> +             if (ret)
> +                     return ret;

And now ioctl(VFIO_IOMMU_GET_INFO) no longer works for any IOMMU
implementing domain_get_attr but not supporting DOMAIN_ATTR_MSI_MAPPING.

> +
> +             if (msi_maps.override_automap) {
> +                     info.flags |= VFIO_IOMMU_INFO_MSI_ALLOW_RECONFIG;
> +                     iommu->allow_msi_reconfig = true;
> +             }
> +
> +             if (msi_maps.automap)
> +                     info.flags |= VFIO_IOMMU_INFO_MSI_AUTOMAP;
> +
>               info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
>  
>               return copy_to_user((void __user *)arg, &info, minsz);
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 1abd1a9..9998f6e 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -391,6 +391,9 @@ struct vfio_iommu_type1_info {
>       __u32   argsz;
>       __u32   flags;
>  #define VFIO_IOMMU_INFO_PGSIZES (1 << 0)     /* supported page sizes info */
> +#define VFIO_IOMMU_INFO_MSI_AUTOMAP (1 << 1) /* MSI pages are auto-mapped
> +                                                in iommu */
> +#define VFIO_IOMMU_INFO_MSI_ALLOW_RECONFIG (1 << 2) /* Allows reconfig 
> automap*/
>       __u64   iova_pgsizes;           /* Bitmap of supported page sizes */
>  };
>  

Once again, exposing interfaces to the user before they actually do
anything is backwards.

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