Dmitry Korotin 0b24cae4d5 MIPS: Add missing EHB in mtc0 -> mfc0 sequence.
Add a missing EHB (Execution Hazard Barrier) in mtc0 -> mfc0 sequence.
Without this execution hazard barrier it's possible for the value read
back from the KScratch register to be the value from before the mtc0.

Reproducible on P5600 & P6600.

The hazard is documented in the MIPS Architecture Reference Manual Vol.
III: MIPS32/microMIPS32 Privileged Resource Architecture (MD00088), rev
6.03 table 8.1 which includes:

   Producer | Consumer | Hazard
  ----------|----------|----------------------------
   mtc0     | mfc0     | any coprocessor 0 register

Signed-off-by: Dmitry Korotin <dkorotin@wavecomp.com>
[paul.burton@mips.com:
  - Commit message tweaks.
  - Add Fixes tags.
  - Mark for stable back to v3.15 where P5600 support was introduced.]
Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: 3d8bfdd030 ("MIPS: Use C0_KScratch (if present) to hold PGD pointer.")
Fixes: 829dcc0a95 ("MIPS: Add MIPS P5600 probe support")
Cc: linux-mips@vger.kernel.org
Cc: stable@vger.kernel.org # v3.15+
2019-06-24 13:43:12 -07:00
2019-06-13 17:34:56 -10:00
…
…
2019-06-16 08:49:45 -10:00

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.
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