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

[K V P, Satyanarayana]

Hi
> -----Original Message-----
> From: Harrison, John C <john.c.harrison at intel.com>
> Sent: Friday, May 23, 2025 1:09 AM
> To: K V P, Satyanarayana <satyanarayana.k.v.p at intel.com>; intel-
> xe at lists.freedesktop.org
> Cc: Wajdeczko, Michal <Michal.Wajdeczko at intel.com>; Nikula, Jani
> <jani.nikula at intel.com>
> Subject: Re: [PATCH v5] drm/xe: Add helper function to inject fault into
> ct_dead_capture()
> 
> 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 at intel.com>
> > Suggested-by: John Harrison <John.C.Harrison at Intel.com>
> > ---
> > Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> > Cc: Jani Nikula <jani.nikula at 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?
We are injecting fault into xe_inject_fault() function which is generic. The fault injection status is obtained from
xe_is_injection_active() function. This is to make function names meaningful.
> 
> >   /**
> >    * 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)