Re: [PATCH v5] drm/xe: Add helper function to inject fault into ct_dead_capture()

[John Harrison <john.c.harrison@intel.com>]

On 5/22/2025 1:00 AM, Satyanarayana K V P wrote:
> When injecting fault to xe_guc_ct_send_recv() & xe_guc_mmio_send_recv()
> functions, the CI test systems are going out of space and crashing. To
> avoid this issue, a new helper function is created and when fault is
> injected into this xe_inject_fault() helper function, ct dead capture
> is avoided which suppresses ct dumps in the log.
>
> Signed-off-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
> Suggested-by: John Harrison <John.C.Harrison@Intel.com>
> ---
> Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
>
> V4 -> V5:
> - Fixed review comments.
>
> V3 -> V4:
> - Updated the name of helper function and moved to xe_device.h file.
>
> V2 -> V3:
> - Added inline function to avoid compilation error in the absence of
> CONFIG_FUNCTION_ERROR_INJECTION.
>
> V1 -> V2:
> - Fixed review comments.
> ---
>   drivers/gpu/drm/xe/xe_device.c | 18 ++++++++++++++++++
>   drivers/gpu/drm/xe/xe_device.h | 14 ++++++++++++++
>   drivers/gpu/drm/xe/xe_guc_ct.c |  6 ++++++
>   3 files changed, 38 insertions(+)
>
> diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
> index 660b0c5126dc..e1b4087a2974 100644
> --- a/drivers/gpu/drm/xe/xe_device.c
> +++ b/drivers/gpu/drm/xe/xe_device.c
> @@ -1120,6 +1120,24 @@ static void xe_device_wedged_fini(struct drm_device *drm, void *arg)
>   	xe_pm_runtime_put(xe);
>   }
>   
> +/**
> + * xe_is_injection_active() - Helper function to test whether a fault
> + * inject test is running.
> + *
> + * This is a helper function that the driver can use to detect whether
> + * a fault injection test is running in order to suppress excessive debug
> + * output. By default, the return value is fixed as zero but it can be modified
> + * by the fault injection framework to return an error.
> + *
> + * Returns:
> + * 0 if no fault is injected.
> + * Injected error if fault is injected.
> + */
> +int xe_is_injection_active(void)
> +{
> +	return xe_inject_fault();
> +}
> +
I'm confused. What is the point of this wrapper?

>   /**
>    * xe_device_declare_wedged - Declare device wedged
>    * @xe: xe device instance
> diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h
> index 0bc3bc8e6803..13a43fe4fb64 100644
> --- a/drivers/gpu/drm/xe/xe_device.h
> +++ b/drivers/gpu/drm/xe/xe_device.h
> @@ -195,6 +195,20 @@ void xe_device_declare_wedged(struct xe_device *xe);
>   struct xe_file *xe_file_get(struct xe_file *xef);
>   void xe_file_put(struct xe_file *xef);
>   
> +#ifdef CONFIG_FUNCTION_ERROR_INJECTION
> +/*
> + * As fault is injected using this function, need to make sure that
> + * the compiler does not optimize and make it as a inline function.
> + * To prevent compile optimization, "noinline" is added.
> + */
> +static noinline int xe_inject_fault(void) { return 0; }
> +ALLOW_ERROR_INJECTION(xe_inject_fault, ERRNO);
> +#else
> +static inline int xe_inject_fault(void) { return 0; }
Why not name this xe_is_injection_active() and just call it directly?

John.

> +#endif
> +
> +int xe_is_injection_active(void);
> +
>   /*
>    * Occasionally it is seen that the G2H worker starts running after a delay of more than
>    * a second even after being queued and activated by the Linux workqueue subsystem. This
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
> index 822f4c33f730..89f992feba31 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> @@ -2040,6 +2040,12 @@ static void ct_dead_capture(struct xe_guc_ct *ct, struct guc_ctb *ctb, u32 reaso
>   
>   	if (ctb)
>   		ctb->info.broken = true;
> +	/*
> +	 * Huge dump is getting generated when injecting error for guc CT/MMIO
> +	 * functions. So, let us suppress the dump when fault is injected.
> +	 */
> +	if (xe_is_injection_active())
> +		return;
>   
>   	/* Ignore further errors after the first dump until a reset */
>   	if (ct->dead.reported)