0a1f57b86c
Sometimes Icelake forgets to reset the CSB pointers on a GPU reset,
leading to it carry on updating the old tail of the buffer.
<0>[ 618.138490] i915_sel-5636 3d..1 673425465us : trace_ports: vecs0: submit { 14de2:504, 0:0 }
<0>[ 618.138490] i915_sel-5636 3.... 673425493us : intel_engine_reset: vecs0 flags=100
<0>[ 618.138490] i915_sel-5636 3.... 673425493us : execlists_reset_prepare: vecs0: depth<-0
<0>[ 618.138490] i915_sel-5636 3.... 673425493us : intel_engine_stop_cs: vecs0
<0>[ 618.138490] i915_sel-5636 3.... 673425523us : __intel_gt_reset: engine_mask=40
<0>[ 618.138490] i915_sel-5636 3.... 673425568us : execlists_reset: vecs0
<0>[ 618.138490] i915_sel-5636 3d..1 673425568us : process_csb: vecs0 cs-irq head=1, tail=2
<0>[ 618.138490] i915_sel-5636 3d..1 673425568us : process_csb: vecs0 csb[2]: status=0x00000001:0x40000000
<0>[ 618.138490] i915_sel-5636 3d..1 673425569us : trace_ports: vecs0: promote { 14de2:504*, 0:0 }
<0>[ 618.138490] i915_sel-5636 3d..1 673425570us : __i915_request_reset: vecs0 rq=14de2:504, guilty? yes
<0>[ 618.138490] i915_sel-5636 3d..1 673425571us : __execlists_reset: vecs0 replay {head:2de0, tail:2e48}
<0>[ 618.138490] i915_sel-5636 3d..1 673425572us : __i915_request_unsubmit: vecs0 fence 14de2:504, current 503
<0>[ 618.138490] i915_sel-5636 3.... 673435544us : intel_engine_cancel_stop_cs: vecs0
<0>[ 618.138490] i915_sel-5636 3.... 673435544us : process_csb: vecs0 cs-irq head=11, tail=11
<0>[ 618.138490] i915_sel-5636 3d..1 673435545us : __i915_request_submit: vecs0 fence 14de2:504, current 503
<0>[ 618.138490] i915_sel-5636 3d..1 673435546us : __execlists_submission_tasklet: vecs0: queue_priority_hint:-2147483648, submit:yes
<0>[ 618.138490] i915_sel-5636 3d..1 673435548us : trace_ports: vecs0: submit { 14de2:504*, 0:0 }
<0>[ 618.138490] i915_sel-5636 3.... 673435549us : execlists_reset_finish: vecs0: depth->0
<0>[ 618.138490] ksoftirq-21 2..s. 673435592us : process_csb: vecs0 cs-irq head=11, tail=3
<0>[ 618.138490] ksoftirq-21 2..s. 673435593us : process_csb: vecs0 csb[0]: status=0x00000001:0x40000000
<0>[ 618.138490] ksoftirq-21 2..s. 673435594us : trace_ports: vecs0: promote { 14de2:504*, 0:0 }
<0>[ 618.138490] ksoftirq-21 2..s. 673435596us : process_csb: vecs0 csb[1]: status=0x00000018:0x40000040
<0>[ 618.138490] ksoftirq-21 2..s. 673435597us : trace_ports: vecs0: completed { 14de2:504*, 0:0 }
<0>[ 618.138490] ksoftirq-21 2..s. 673435612us : process_csb: process_csb:2188 GEM_BUG_ON(!i915_request_completed(*execlists->active) && !reset_in_progress(execlists))
After the reset, we do another clflush before checking the CSB to be
sure we see whatever was left in the CSB prior to the reset. So it is
unlikely to be an incoherent view of the CSB, and more likely that
Icelake didn't reset its pointers.
References: 582a6f90aa0d ("drm/i915/execlists: Add a paranoid flush of the CSB pointers upon reset")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191104135307.21083-1-chris@chris-wilson.co.uk
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.