> -----Original Message----- > From: Chris Wilson [mailto:chris@xxxxxxxxxxxxxxxxxx] > Sent: Wednesday, December 6, 2017 7:38 AM > To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>; Bloomfield, Jon > <jon.bloomfield@xxxxxxxxx>; Harrison, John C <john.c.harrison@xxxxxxxxx>; > Ursulin, Tvrtko <tvrtko.ursulin@xxxxxxxxx>; Joonas Lahtinen > <joonas.lahtinen@xxxxxxxxxxxxxxx>; Daniel Vetter <daniel.vetter@xxxxxxxx> > Subject: [PATCH v2] drm/i915: Prevent machine hang from Broxton's vtd w/a > and error capture > > Since capturing the error state requires fiddling around with the GGTT > to read arbitrary buffers and is itself run under stop_machine(), it > deadlocks the machine (effectively a hard hang) when run in conjunction > with Broxton's VTd workaround to serialize GGTT access. > > v2: Store the ERR_PTR in first_error so that the error can be reported > to the user via sysfs. > > Fixes: 0ef34ad6222a ("drm/i915: Serialize GTT/Aperture accesses on BXT") > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Cc: Jon Bloomfield <jon.bloomfield@xxxxxxxxx> > Cc: John Harrison <john.C.Harrison@xxxxxxxxx> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> It's a real shame to lose error capture on BXT. Can we wrap stop_machine to make it recursive ? Something like... static cpumask_t sm_mask; struct sm_args { cpu_stop_fn_t *fn; void *data; }; void do_recursive_stop(void *sm_arg_data) { struct sm_arg *args = sm_arg_data; /* We're stopped - flag the fact to prevent recursion */ cpumask_set_cpu(smp_processor_id(), &sm_mask); args->fn(args->data); /* Re-enable recursion */ cpumask_clear_cpu(smp_processor_id(), &sm_mask); } void recursive_stop_machine(cpu_stop_fn_t fn, void *data) { if (cpumask_test_cpu(smp_processor_id(), &sm_mask)) { /* We were already stopped, so can just call directly */ fn(data); } else { /* Our CPU is not currently stopped */ struct sm_args *args = {fn, data}; stop_machine(do_recursive_stop, args, NULL); } } _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
