Re: [PATCH v2 3/3] RFC drm/xe: add fault injection for lmem init check

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Fri, Mar 15, 2024 at 03:35:30PM +0530, Riana Tauro wrote:
> add a boot time fault injection for lmem init check.
> This can be triggered by adding a modparam fail_lmem_init
> 
> xe.fail_lmem_init=<interval>,<probability>,<space>,<times>

Please let's avoid module parameters as much as we can.

Let's use the CONFIG_FAULT_INJECTION_DEBUG_FS
similarly to

fault_create_debugfs_attr("fail_gt_reset", root, &gt_reset_f\
ailure);

And then use it like this:

https://lore.kernel.org/all/20240315010843.194335-1-rodrigo.vivi@intel.com/

> 
> Adding this causes the lmem init check to fail causing
> the probe to defer.
> 
> v2: add fault injection (Lucas)
> 
> Signed-off-by: Riana Tauro <riana.tauro@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_device.c | 21 +++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_module.c |  5 +++++
>  drivers/gpu/drm/xe/xe_module.h |  3 +++
>  3 files changed, 29 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
> index 50473329cce7..393610e95bd1 100644
> --- a/drivers/gpu/drm/xe/xe_device.c
> +++ b/drivers/gpu/drm/xe/xe_device.c
> @@ -51,6 +51,10 @@ struct lockdep_map xe_device_mem_access_lockdep_map = {
>  };
>  #endif
>  
> +#ifdef CONFIG_FAULT_INJECTION
> +DECLARE_FAULT_ATTR(lmem_init_fail);
> +#endif
> +
>  static int xe_file_open(struct drm_device *dev, struct drm_file *file)
>  {
>  	struct xe_device *xe = to_xe_device(dev);
> @@ -431,6 +435,23 @@ static int wait_for_lmem_ready(struct xe_device *xe)
>  	if (IS_SRIOV_VF(xe))
>  		return 0;
>  
> +#ifdef CONFIG_FAULT_INJECTION
> +	/*
> +	 * use fault injection to cause a lmem init failure to validate
> +	 * deferred probe. Set the verbose to 0 to  avoid dump stack
> +	 */
> +	if (xe_modparam.fail_lmem_init) {
> +		setup_fault_attr(&lmem_init_fail, xe_modparam.fail_lmem_init);
> +		lmem_init_fail.verbose = 0;
> +		if (should_fail(&lmem_init_fail, 1)) {
> +			/* add delay to reduce the number of deferred probe attempts */
> +			msleep(500);
> +			drm_dbg(&xe->drm, "Fault Injection lmem init failure\n");
> +			return -EPROBE_DEFER;
> +		}
> +	}
> +#endif
> +
>  	if (verify_lmem_ready(gt))
>  		return 0;
>  
> diff --git a/drivers/gpu/drm/xe/xe_module.c b/drivers/gpu/drm/xe/xe_module.c
> index 110b69864656..c4efbab430a7 100644
> --- a/drivers/gpu/drm/xe/xe_module.c
> +++ b/drivers/gpu/drm/xe/xe_module.c
> @@ -48,6 +48,11 @@ module_param_named_unsafe(force_probe, xe_modparam.force_probe, charp, 0400);
>  MODULE_PARM_DESC(force_probe,
>  		 "Force probe options for specified devices. See CONFIG_DRM_XE_FORCE_PROBE for details.");
>  
> +#ifdef CONFIG_FAULT_INJECTION
> +module_param_named_unsafe(fail_lmem_init, xe_modparam.fail_lmem_init, charp, 0400);
> +MODULE_PARM_DESC(fail_lmem_init, "Fault injection. fail_lmem_init=<interval>,<probability>,<space>,<times>");
> +#endif
> +
>  struct init_funcs {
>  	int (*init)(void);
>  	void (*exit)(void);
> diff --git a/drivers/gpu/drm/xe/xe_module.h b/drivers/gpu/drm/xe/xe_module.h
> index 88ef0e8b2bfd..ccbeacbc3efb 100644
> --- a/drivers/gpu/drm/xe/xe_module.h
> +++ b/drivers/gpu/drm/xe/xe_module.h
> @@ -18,6 +18,9 @@ struct xe_modparam {
>  	char *huc_firmware_path;
>  	char *gsc_firmware_path;
>  	char *force_probe;
> +#if IS_ENABLED(CONFIG_FAULT_INJECTION)
> +	char *fail_lmem_init;
> +#endif /* CONFIG_FAULT_INJECTION */
>  };
>  
>  extern struct xe_modparam xe_modparam;
> -- 
> 2.40.0
>