Re: [PATCH v2] drm/xe: Work around clang multiple goto-label error

[Nathan Chancellor <nathan@kernel.org>]

On Thu, Sep 11, 2025 at 10:03:24AM +0200, Thomas Hellström wrote:
> When using drm_exec_retry_on_contention(), clang may consider
> all labels for which we take addresses in a function as
> potential retry goto targets, although strictly only one
> is possible. It will then in some situations generate false
> positive errors.
> 
> In this case, the compiler, for some architectures, consider the
> 
> might_lock(&m->job_mutex);
> 
> as a potential goto target from drm_exec_retry_on_contention(),
> and errors.
> 
> Work around that by moving the xe_validate / drm_exec
> transaction to a separate function.
> 
> v2:
> - New commit message based on analysis of Nathan Chancellor
> 
> Fixes: 59eabff2a352 ("drm/xe: Convert xe_bo_create_pin_map() for exhaustive eviction")
> Cc: Matthew Brost <matthew.brost@intel.com>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202509101853.nDmyxTEM-lkp@intel.com/
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org> # build

> ---
>  drivers/gpu/drm/xe/xe_migrate.c | 29 +++++++++++++++++++----------
>  1 file changed, 19 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
> index 6fad5d469629..1d667fa36cf3 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -394,6 +394,24 @@ struct xe_migrate *xe_migrate_alloc(struct xe_tile *tile)
>  	return m;
>  }
>  
> +static int xe_migrate_lock_prepare_vm(struct xe_tile *tile, struct xe_migrate *m, struct xe_vm *vm)
> +{
> +	struct xe_device *xe = tile_to_xe(tile);
> +	struct xe_validation_ctx ctx;
> +	struct drm_exec exec;
> +	int err = 0;
> +
> +	xe_validation_guard(&ctx, &xe->val, &exec, (struct xe_val_flags) {}, err) {
> +		err = xe_vm_drm_exec_lock(vm, &exec);
> +		drm_exec_retry_on_contention(&exec);
> +		err = xe_migrate_prepare_vm(tile, m, vm, &exec);
> +		drm_exec_retry_on_contention(&exec);
> +		xe_validation_retry_on_oom(&ctx, &err);
> +	}
> +
> +	return err;
> +}
> +
>  /**
>   * xe_migrate_init() - Initialize a migrate context
>   * @m: The migration context
> @@ -405,8 +423,6 @@ int xe_migrate_init(struct xe_migrate *m)
>  	struct xe_tile *tile = m->tile;
>  	struct xe_gt *primary_gt = tile->primary_gt;
>  	struct xe_device *xe = tile_to_xe(tile);
> -	struct xe_validation_ctx ctx;
> -	struct drm_exec exec;
>  	struct xe_vm *vm;
>  	int err;
>  
> @@ -416,14 +432,7 @@ int xe_migrate_init(struct xe_migrate *m)
>  	if (IS_ERR(vm))
>  		return PTR_ERR(vm);
>  
> -	err = 0;
> -	xe_validation_guard(&ctx, &xe->val, &exec, (struct xe_val_flags) {}, err) {
> -		err = xe_vm_drm_exec_lock(vm, &exec);
> -		drm_exec_retry_on_contention(&exec);
> -		err = xe_migrate_prepare_vm(tile, m, vm, &exec);
> -		drm_exec_retry_on_contention(&exec);
> -		xe_validation_retry_on_oom(&ctx, &err);
> -	}
> +	err = xe_migrate_lock_prepare_vm(tile, m, vm);
>  	if (err)
>  		return err;
>  
> -- 
> 2.51.0
>