[Bug 104708] [IGT] igt at gem_exec_flush@* BUG: unable to handle kernel paging request at 0000000100000084
bugzilla-daemon at freedesktop.org
bugzilla-daemon at freedesktop.org
Wed Aug 22 13:30:25 UTC 2018
https://bugs.freedesktop.org/show_bug.cgi?id=104708
Lakshmi <lakshminarayana.vudum at intel.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |CLOSED
--- Comment #17 from Lakshmi <lakshminarayana.vudum at intel.com> ---
(In reply to Chris Wilson from comment #16)
> commit 77dfedb5be03779f9a5d83e323a1b36e32090105
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date: Fri May 11 13:11:45 2018 +0100
>
> drm/i915/execlists: Use rmb() to order CSB reads
>
> We assume that the CSB is written using the normal ringbuffer
> coherency protocols, as outlined in kernel/events/ring_buffer.c:
>
> * (HW) (DRIVER)
> *
> * if (LOAD ->data_tail) { LOAD ->data_head
> * (A) smp_rmb() (C)
> * STORE $data LOAD $data
> * smp_wmb() (B) smp_mb() (D)
> * STORE ->data_head STORE ->data_tail
> * }
>
> So we assume that the HW fulfils its ordering requirements (B), and so
> we should use a complimentary rmb (C) to ensure that our read of its
> WRITE pointer is completed before we start accessing the data.
>
> The final mb (D) is implied by the uncached mmio we perform to inform
> the HW of our READ pointer.
>
> References: https://bugs.freedesktop.org/show_bug.cgi?id=105064
> References: https://bugs.freedesktop.org/show_bug.cgi?id=105888
> References: https://bugs.freedesktop.org/show_bug.cgi?id=106185
> Fixes: 767a983ab255 ("drm/i915/execlists: Read the context-status HEAD
> from the HWSP")
> References: 61bf9719fa17 ("drm/i915/cnl: Use mmio access to context
> status buffer")
> Suggested-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: MichaĆ Winiarski <michal.winiarski at intel.com>
> Cc: Rafael Antognolli <rafael.antognolli at intel.com>
> Cc: Michel Thierry <michel.thierry at intel.com>
> Cc: Timo Aaltonen <tjaalton at ubuntu.com>
> Tested-by: Timo Aaltonen <tjaalton at ubuntu.com>
> Acked-by: Michel Thierry <michel.thierry at intel.com>
> Acked-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Link:
> https://patchwork.freedesktop.org/patch/msgid/20180511121147.31915-1-
> chris at chris-wilson.co.uk
Closing this issue as this was already resolved and verified.
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