Re: [PATCH v2] drm/xe/ufence: Flush xe ordered_wq in case of ufence timeout

[Matthew Brost <matthew.brost@intel.com>]

On Thu, Oct 24, 2024 at 10:14:21AM -0700, John Harrison wrote:
> On 10/24/2024 08:18, Nirmoy Das wrote:
> > Flush xe ordered_wq in case of ufence timeout which is observed
> > on LNL and that points to the recent scheduling issue with E-cores.
> > 
> > This is similar to the recent fix:
> > commit e51527233804 ("drm/xe/guc/ct: Flush g2h worker in case of g2h
> > response timeout") and should be removed once there is E core
> > scheduling fix.
> > 
> > v2: Add platform check(Himal)
> >      s/__flush_workqueue/flush_workqueue(Jani)
> > 
> > Cc: Badal Nilawar <badal.nilawar@intel.com>
> > Cc: Jani Nikula <jani.nikula@intel.com>
> > Cc: Matthew Auld <matthew.auld@intel.com>
> > Cc: John Harrison <John.C.Harrison@Intel.com>
> > Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> > Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> > Cc: <stable@vger.kernel.org> # v6.11+
> > Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/2754
> > Suggested-by: Matthew Brost <matthew.brost@intel.com>
> > Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> > Reviewed-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> >   drivers/gpu/drm/xe/xe_wait_user_fence.c | 14 ++++++++++++++
> >   1 file changed, 14 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_wait_user_fence.c b/drivers/gpu/drm/xe/xe_wait_user_fence.c
> > index f5deb81eba01..78a0ad3c78fe 100644
> > --- a/drivers/gpu/drm/xe/xe_wait_user_fence.c
> > +++ b/drivers/gpu/drm/xe/xe_wait_user_fence.c
> > @@ -13,6 +13,7 @@
> >   #include "xe_device.h"
> >   #include "xe_gt.h"
> >   #include "xe_macros.h"
> > +#include "compat-i915-headers/i915_drv.h"
> >   #include "xe_exec_queue.h"
> >   static int do_compare(u64 addr, u64 value, u64 mask, u16 op)
> > @@ -155,6 +156,19 @@ int xe_wait_user_fence_ioctl(struct drm_device *dev, void *data,
> >   		}
> >   		if (!timeout) {
> > +			if (IS_LUNARLAKE(xe)) {
> > +				/*
> > +				 * This is analogous to e51527233804 ("drm/xe/guc/ct: Flush g2h
> > +				 * worker in case of g2h response timeout")
> > +				 *
> > +				 * TODO: Drop this change once workqueue scheduling delay issue is
> > +				 * fixed on LNL Hybrid CPU.
> > +				 */
> > +				flush_workqueue(xe->ordered_wq);
> If we are having multiple instances of this workaround, can we wrap them up
> in as 'LNL_FLUSH_WORKQUEUE(q)' or some such? Put the IS_LNL check inside the
> macro and make it pretty obvious exactly where all the instances are by
> having a single macro name to search for.
> 

+1, I think Lucas is suggesting something similar to this on the chat to
make sure we don't lose track of removing these W/A when this gets
fixed.

Matt

> John.
> 
> > +				err = do_compare(addr, args->value, args->mask, args->op);
> > +				if (err <= 0)
> > +					break;
> > +			}
> >   			err = -ETIME;
> >   			break;
> >   		}
>