Re: [XEN][PATCH v10 10/20] xen/iommu: protect iommu_add_dt_device() with dtdevs_lock

[Vikram Garhwal <vikram.garhwal@amd.com>]

On Fri, Aug 25, 2023 at 01:02:12AM -0700, Vikram Garhwal wrote:
> Protect iommu_add_dt_device() with dtdevs_lock to prevent concurrent access
> to add/remove/assign/deassign.
> With addition of dynamic programming feature(follow-up patches in this series),
> this function can be concurrently accessed by while making a device
> assign/deassign for passthrough and by dynamic node add/remove using device tree
> overlays.
There was a comment from Julien on v9 on commit message. In v11, I Will remove
references to PCI because this is misleading.
> 
> Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
> Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
> Reviewed-by: Michal Orzel <michal.orzel@amd.com>
> 
> ---
>     Changes from v7:
>         Update commit message and fix indent.
> ---
> ---
>  xen/drivers/passthrough/device_tree.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/drivers/passthrough/device_tree.c b/xen/drivers/passthrough/device_tree.c
> index 5d84c07b50..1202eac625 100644
> --- a/xen/drivers/passthrough/device_tree.c
> +++ b/xen/drivers/passthrough/device_tree.c
> @@ -148,6 +148,8 @@ int iommu_add_dt_device(struct dt_device_node *np)
>      if ( dev_iommu_fwspec_get(dev) )
>          return 0;
>  
> +    spin_lock(&dtdevs_lock);
> +
>      /*
>       * According to the Documentation/devicetree/bindings/iommu/iommu.txt
>       * from Linux.
> @@ -160,7 +162,10 @@ int iommu_add_dt_device(struct dt_device_node *np)
>           * these callback implemented.
>           */
>          if ( !ops->add_device || !ops->dt_xlate )
> -            return -EINVAL;
> +        {
> +            rc = -EINVAL;
> +            goto fail;
> +        }
>  
>          if ( !dt_device_is_available(iommu_spec.np) )
>              break;
> @@ -191,6 +196,8 @@ int iommu_add_dt_device(struct dt_device_node *np)
>      if ( rc < 0 )
>          iommu_fwspec_free(dev);
>  
> + fail:
> +    spin_unlock(&dtdevs_lock);
>      return rc;
>  }
>  
> -- 
> 2.17.1
> 
>