Re: [Intel-xe] [PATCH] drm/xe: don't auto fall back to execlist mode if guc failed to init

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Fri, Mar 24, 2023 at 12:15:27PM -0400, Rodrigo Vivi wrote:
> On Thu, Mar 23, 2023 at 11:08:58PM +0000, Chang, Yu bruce wrote:
> >
> >
> > > -----Original Message-----
> > > From: Brost, Matthew <matthew.brost@intel.com>
> > > Sent: Thursday, March 23, 2023 3:53 PM
> > > To: Chang, Yu bruce <yu.bruce.chang@intel.com>
> > > Cc: intel-xe@lists.freedesktop.org
> > > Subject: Re: [Intel-xe] [PATCH] drm/xe: don't auto fall back to execlist mode
> > > if guc failed to init
> > >
> > > On Thu, Mar 23, 2023 at 08:23:13PM +0000, Chang, Bruce wrote:
> > > > In general, this is due to FW load failure, should just report error
> > > > and fail the probe so that user can easily retry again.
> > > >
> > > > Cc: Matt Roper <matthew.d.roper@intel.com>
> > > > Signed-off-by: Bruce Chang <yu.bruce.chang@intel.com>
> > >
> > > I have not tested this but assuming you did:
> > > Reviewed-by: Matthew Brost <matthew.brost@intel.com>
> > >
> > Yes, I tested on PVC and it used to fall back to execlist mode and constantly
> > print out EXECLIST_STATUS. Now all those are not showing after this change.
>
> But now the entire execlist code is bogus.
> We should remove it entirely or at least add a parameter that allows
> that to be selected.

:( My comment was entirely ignored and the patch was pushed.
Well, I complained about dead code...

after removing the fallback we need to either add a paremeter or kill
execlists entirely. My preference is for killing that entirely.

But also I just notice that this patch actually only does half of
disabling the fallback.

When fw is not found we still have the fallback in place:

@xe_uc_init:
err:
        /* If any uC firmwares not found, fall back to execlists */
        xe_device_guc_submission_disable(uc_to_xe(uc));

>
> >
> > There is still other unrelated issues during __pfx_ggtt_fini_noalloc, and need
> > to be fixed as below.
> >
> > [  223.839894] BUG: KASAN: null-ptr-deref in ttm_resource_free+0xe4/0x140 [ttm]
> > [  223.847211] Read of size 8 at addr 0000000000000018 by task systemd-udevd/566
> >
> > [  223.856141] CPU: 0 PID: 566 Comm: systemd-udevd Not tainted 6.2.0-xe+ #4
> > [  223.864921] Hardware name: Intel Corporation WilsonCity/WilsonCity, BIOS WLYDCRB1.SYS.0020.P84.2103030140 03/03/2021
> > [  223.877365] Call Trace:
> > [  223.881707]  <TASK>
> > [  223.885658]  dump_stack_lvl+0x5b/0x85
> > [  223.891200]  print_report+0x499/0x4aa
> > [  223.896690]  ? ttm_resource_free+0xe4/0x140 [ttm]
> > [  223.903268]  kasan_report+0x99/0x1a0
> > [  223.908683]  ? ttm_resource_free+0xe4/0x140 [ttm]
> > [  223.915210]  ttm_resource_free+0xe4/0x140 [ttm]
> > [  223.921621]  ttm_bo_release+0x3e5/0x550 [ttm]
> > [  223.927811]  ? __pfx_ttm_bo_release+0x10/0x10 [ttm]
> > [  223.934530]  ? ttm_bo_kunmap+0x11f/0x160 [ttm]
> > [  223.940775]  ? __pfx_ggtt_fini_noalloc+0x10/0x10 [xe]
> >
> > > > ---
> > > >  drivers/gpu/drm/xe/xe_gt.c | 4 ++--
> > > >  drivers/gpu/drm/xe/xe_uc.c | 3 ---
> > > >  2 files changed, 2 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/xe/xe_gt.c b/drivers/gpu/drm/xe/xe_gt.c
> > > > index daa433d0f2f5..8a436c95591e 100644
> > > > --- a/drivers/gpu/drm/xe/xe_gt.c
> > > > +++ b/drivers/gpu/drm/xe/xe_gt.c
> > > > @@ -455,9 +455,9 @@ static int gt_fw_domain_init(struct xe_gt *gt)
> > > >  			goto err_force_wake;
> > > >  	}
> > > >
> > > > -	/* Allow driver to load if uC init fails (likely missing firmware) */
> > > >  	err = xe_uc_init(&gt->uc);
> > > > -	XE_WARN_ON(err);
> > > > +	if (err)
> > > > +		goto err_force_wake;
> > > >
> > > >  	err = xe_uc_init_hwconfig(&gt->uc);
> > > >  	if (err)
> > > > diff --git a/drivers/gpu/drm/xe/xe_uc.c b/drivers/gpu/drm/xe/xe_uc.c
> > > > index 4ccf2b3435e1..70eabf567156 100644
> > > > --- a/drivers/gpu/drm/xe/xe_uc.c
> > > > +++ b/drivers/gpu/drm/xe/xe_uc.c
> > > > @@ -54,9 +54,6 @@ int xe_uc_init(struct xe_uc *uc)
> > > >  	return 0;
> > > >
> > > >  err:
> > > > -	/* If any uC firmwares not found, fall back to execlists */
> > > > -	xe_device_guc_submission_disable(uc_to_xe(uc));
> > > > -
> > > >  	return ret;
> > > >  }
> > > >
> > > > --
> > > > 2.25.1
> > > >