On Tue, Jan 07, 2025 at 05:34:20PM -0800, Abhinav Kumar wrote:
>
>
> On 12/18/2024 1:33 PM, Jessica Zhang wrote:
> >
> >
> > On 12/18/2024 3:20 AM, Dmitry Baryshkov wrote:
> > > On Tue, Dec 17, 2024 at 04:27:57PM -0800, Jessica Zhang wrote:
> > > > From: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> > > >
> > > > There is no recovery mechanism in place yet to recover from mmu
> > > > faults for DPU. We can only prevent the faults by making sure there
> > > > is no misconfiguration.
> > > >
> > > > Rate-limit the snapshot capture for mmu faults to once per
> > > > msm_atomic_commit_tail() as that should be sufficient to capture
> > > > the snapshot for debugging otherwise there will be a lot of DPU
> > > > snapshots getting captured for the same fault which is redundant
> > > > and also might affect capturing even one snapshot accurately.
> > > >
> > > > Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> > > > Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
> > > > ---
> > > > drivers/gpu/drm/msm/msm_atomic.c | 2 ++
> > > > drivers/gpu/drm/msm/msm_kms.c | 5 ++++-
> > > > drivers/gpu/drm/msm/msm_kms.h | 3 +++
> > > > 3 files changed, 9 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/msm/msm_atomic.c
> > > > b/drivers/gpu/drm/msm/msm_atomic.c
> > > > index 9c45d641b5212c11078ab38c13a519663d85e10a..9ad7eeb14d4336abd9d8a8eb1382bdddce80508a
> > > > 100644
> > > > --- a/drivers/gpu/drm/msm/msm_atomic.c
> > > > +++ b/drivers/gpu/drm/msm/msm_atomic.c
> > > > @@ -228,6 +228,8 @@ void msm_atomic_commit_tail(struct
> > > > drm_atomic_state *state)
> > > > if (kms->funcs->prepare_commit)
> > > > kms->funcs->prepare_commit(kms, state);
> > > > + kms->fault_snapshot_capture = 0;
> > > > +
> > >
> > > - Please move it before the prepare_commit().
> > > - You are accessing the same variable from different threads / cores.
> > > There should be some kind of a sync barrier.
> >
> > Hi Dmitry,
> >
> > Ack, will add a lock for the snapshot capture counter.
> >
> > Thanks,
> >
> > Jessica Zhang
> >
>
> We cannot have a mutex lock because msm_kms_fault_handler cannot hold a
> mutex. So we need an atomic variable in this case.
Or a spinlock.
>
> > >
> > > > /*
> > > > * Push atomic updates down to hardware:
> > > > */
> > > > diff --git a/drivers/gpu/drm/msm/msm_kms.c
> > > > b/drivers/gpu/drm/msm/msm_kms.c
> > > > index 78830e446355f77154fa21a5d107635bc88ba3ed..3327caf396d4fc905dc127f09515559c12666dc8
> > > > 100644
> > > > --- a/drivers/gpu/drm/msm/msm_kms.c
> > > > +++ b/drivers/gpu/drm/msm/msm_kms.c
> > > > @@ -168,7 +168,10 @@ static int msm_kms_fault_handler(void *arg,
> > > > unsigned long iova, int flags, void
> > > > {
> > > > struct msm_kms *kms = arg;
> > > > - msm_disp_snapshot_state(kms->dev);
> > > > + if (!kms->fault_snapshot_capture) {
> > > > + msm_disp_snapshot_state(kms->dev);
> > > > + kms->fault_snapshot_capture++;
> > > > + }
> > > > return -ENOSYS;
> > > > }
> > > > diff --git a/drivers/gpu/drm/msm/msm_kms.h
> > > > b/drivers/gpu/drm/msm/msm_kms.h
> > > > index e60162744c669773b6e5aef824a173647626ab4e..3ac089e26e14b824567f3cd2c62f82a1b9ea9878
> > > > 100644
> > > > --- a/drivers/gpu/drm/msm/msm_kms.h
> > > > +++ b/drivers/gpu/drm/msm/msm_kms.h
> > > > @@ -128,6 +128,9 @@ struct msm_kms {
> > > > int irq;
> > > > bool irq_requested;
> > > > + /* rate limit the snapshot capture to once per attach */
> > > > + int fault_snapshot_capture;
> > > > +
> > > > /* mapper-id used to request GEM buffer mapped for scanout: */
> > > > struct msm_gem_address_space *aspace;
> > > >
> > > > --
> > > > 2.34.1
> > > >
> > >
> > > --
> > > With best wishes
> > > Dmitry
> >
--
With best wishes
Dmitry
