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

[Riana Tauro <riana.tauro@intel.com>]

Hi Rodrigo

On 3/19/2024 2:45 AM, Rodrigo Vivi wrote:
> 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);
> 
lmem init check is done during early probe. We cannot set debugfs before 
probe completes. So i added the module parameter.

I can try to set static values before injecting fault if module param is 
not needed.

lmem_init_fail.times = 1;
lmem_init_fail.probability = 100;

Thanks
Riana
> 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
>>