Re: [XEN][RFC PATCH v4 07/16] xen/iommu: Move spin_lock from iommu_dt_device_is_assigned to caller

[Michal Orzel <michal.orzel@amd.com>]

Hi Vikram,

On 07/12/2022 07:18, Vikram Garhwal wrote:
> 
> 
> Rename iommu_dt_device_is_assigned() to iommu_dt_device_is_assigned_lock().
s/lock/locked/

> 
> Moving spin_lock to caller was done to prevent the concurrent access to
> iommu_dt_device_is_assigned while doing add/remove/assign/deassign.
> 
> Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
> Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
> ---
>  xen/drivers/passthrough/device_tree.c | 23 +++++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/device_tree.c b/xen/drivers/passthrough/device_tree.c
> index 1c32d7b50c..bb4cf7784d 100644
> --- a/xen/drivers/passthrough/device_tree.c
> +++ b/xen/drivers/passthrough/device_tree.c
> @@ -83,16 +83,15 @@ fail:
>      return rc;
>  }
> 
> -static bool_t iommu_dt_device_is_assigned(const struct dt_device_node *dev)
> +static bool_t
> +    iommu_dt_device_is_assigned_locked(const struct dt_device_node *dev)
This should not be indented
>  {
>      bool_t assigned = 0;
> 
>      if ( !dt_device_is_protected(dev) )
>          return 0;
> 
> -    spin_lock(&dtdevs_lock);
>      assigned = !list_empty(&dev->domain_list);
> -    spin_unlock(&dtdevs_lock);
> 
>      return assigned;
>  }
> @@ -213,27 +212,43 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d,
>          if ( (d && d->is_dying) || domctl->u.assign_device.flags )
>              break;
> 
> +        spin_lock(&dtdevs_lock);
> +
>          ret = dt_find_node_by_gpath(domctl->u.assign_device.u.dt.path,
>                                      domctl->u.assign_device.u.dt.size,
>                                      &dev);
>          if ( ret )
> +        {
> +            spin_unlock(&dtdevs_lock);
> +
I think removing a blank line here and in other places would look better.

~Michal