Re: [Intel-xe] [PATCH v3 1/3] drm/xe: Store xe_he_engine in xe_hw_engine_snapshot

["Souza, Jose" <jose.souza@intel.com>]

On Thu, 2023-10-12 at 10:16 -0700, Matt Roper wrote:
> On Tue, Oct 10, 2023 at 11:41:49AM -0700, José Roberto de Souza wrote:
> > A future patch will require gt and xe device structs, so here
> > replacing class by hwe.
> > 
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > Cc: Matt Roper <matthew.d.roper@intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > ---
> >  drivers/gpu/drm/xe/xe_hw_engine.c       | 6 +++---
> >  drivers/gpu/drm/xe/xe_hw_engine_types.h | 4 ++--
> >  2 files changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_hw_engine.c b/drivers/gpu/drm/xe/xe_hw_engine.c
> > index b5b0845908887..37b3ee1268090 100644
> > --- a/drivers/gpu/drm/xe/xe_hw_engine.c
> > +++ b/drivers/gpu/drm/xe/xe_hw_engine.c
> > @@ -684,7 +684,7 @@ xe_hw_engine_snapshot_capture(struct xe_hw_engine *hwe)
> >  	if (snapshot->name)
> >  		strscpy(snapshot->name, hwe->name, len);
> >  
> > -	snapshot->class = hwe->class;
> > +	snapshot->hwe = hwe;
> 
> I haven't really looked into the devcoredump stuff much, but it's not
> clear to me from a really quick skim whether it's safe to save away the
> hwe like this.  Is there ever a case where the snapshot can persist
> after the engine itself has been destroyed (e.g., if we capture an error
> encountered during a device probe that results in the device being torn
> back down)?  If so, then you'd probably need to make sure that the hwe
> field here only gets used during the capture, and the 'print' routine
> would still need a cached snapshot->class to avoid use-after-free
> errors.

Xe devcoredump dump is also removed with Xe module, so no problems with this.

> 
> Rodrigo probably has better insight as to whether that's something that
> we need to worry about.
> 
> 
> Matt
> 
> >  	snapshot->logical_instance = hwe->logical_instance;
> >  	snapshot->forcewake.domain = hwe->domain;
> >  	snapshot->forcewake.ref = xe_force_wake_ref(gt_to_fw(hwe->gt),
> > @@ -731,7 +731,7 @@ xe_hw_engine_snapshot_capture(struct xe_hw_engine *hwe)
> >  		hw_engine_mmio_read32(hwe, RING_DMA_FADD(0));
> >  	snapshot->reg.ipehr = hw_engine_mmio_read32(hwe, RING_IPEHR(0));
> >  
> > -	if (snapshot->class == XE_ENGINE_CLASS_COMPUTE)
> > +	if (snapshot->hwe->class == XE_ENGINE_CLASS_COMPUTE)
> >  		snapshot->reg.rcu_mode = xe_mmio_read32(hwe->gt, RCU_MODE);
> >  
> >  	return snapshot;
> > @@ -786,7 +786,7 @@ void xe_hw_engine_snapshot_print(struct xe_hw_engine_snapshot *snapshot,
> >  		   snapshot->reg.ring_dma_fadd_udw,
> >  		   snapshot->reg.ring_dma_fadd);
> >  	drm_printf(p, "\tIPEHR: 0x%08x\n\n", snapshot->reg.ipehr);
> > -	if (snapshot->class == XE_ENGINE_CLASS_COMPUTE)
> > +	if (snapshot->hwe->class == XE_ENGINE_CLASS_COMPUTE)
> >  		drm_printf(p, "\tRCU_MODE: 0x%08x\n",
> >  			   snapshot->reg.rcu_mode);
> >  }
> > diff --git a/drivers/gpu/drm/xe/xe_hw_engine_types.h b/drivers/gpu/drm/xe/xe_hw_engine_types.h
> > index 5d4ee29042407..71c0a0169e62a 100644
> > --- a/drivers/gpu/drm/xe/xe_hw_engine_types.h
> > +++ b/drivers/gpu/drm/xe/xe_hw_engine_types.h
> > @@ -156,8 +156,8 @@ struct xe_hw_engine {
> >  struct xe_hw_engine_snapshot {
> >  	/** @name: name of the hw engine */
> >  	char *name;
> > -	/** @class: class of this hw engine */
> > -	enum xe_engine_class class;
> > +	/** @hwe: hw engine */
> > +	struct xe_hw_engine *hwe;
> >  	/** @logical_instance: logical instance of this hw engine */
> >  	u16 logical_instance;
> >  	/** @forcewake: Force Wake information snapshot */
> > -- 
> > 2.42.0
> > 
>