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Paul Burton b42aa3fd59
MIPS: tlbex: Fix build_restore_pagemask KScratch restore 
build_restore_pagemask() will restore the value of register $1/$at when
its restore_scratch argument is non-zero, and aims to do so by filling a
branch delay slot. Commit 0b24cae4d5 ("MIPS: Add missing EHB in mtc0
-> mfc0 sequence.") added an EHB instruction (Execution Hazard Barrier)
prior to restoring $1 from a KScratch register, in order to resolve a
hazard that can result in stale values of the KScratch register being
observed. In particular, P-class CPUs from MIPS with out of order
execution pipelines such as the P5600 & P6600 are affected.

Unfortunately this EHB instruction was inserted in the branch delay slot
causing the MFC0 instruction which performs the restoration to no longer
execute along with the branch. The result is that the $1 register isn't
actually restored, ie. the TLB refill exception handler clobbers it -
which is exactly the problem the EHB is meant to avoid for the P-class
CPUs.

Similarly build_get_pgd_vmalloc() will restore the value of $1/$at when
its mode argument equals refill_scratch, and suffers from the same
problem.

Fix this by in both cases moving the EHB earlier in the emitted code.
There's no reason it needs to immediately precede the MFC0 - it simply
needs to be between the MTC0 & MFC0.

This bug only affects Cavium Octeon systems which use
build_fast_tlb_refill_handler().

Signed-off-by: Paul Burton <paulburton@kernel.org>
Fixes: 0b24cae4d5 ("MIPS: Add missing EHB in mtc0 -> mfc0 sequence.")
Cc: Dmitry Korotin <dkorotin@wavecomp.com>
Cc: stable@vger.kernel.org # v3.15+
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
 		2019-10-23 21:12:49 -07:00
Documentation hwmon fixes for v5.4-rc3 2019-10-13 08:40:31 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch MIPS: tlbex: Fix build_restore_pagemask KScratch restore 2019-10-23 21:12:49 -07:00
block blk-wbt: fix performance regression in wbt scale_up/scale_down 2019-10-06 09:26:41 -06:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-09-28 08:14:15 -07:00
drivers hwmon fixes for v5.4-rc3 2019-10-13 08:40:31 -07:00
fs A few tracing fixes: 2019-10-13 14:47:10 -07:00
include hwmon fixes for v5.4-rc3 2019-10-13 08:40:31 -07:00
init Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-09-28 08:14:15 -07:00
ipc ipc/sem.c: convert to use built-in RCU list checking 2019-09-25 17:51:41 -07:00
kernel A few tracing fixes: 2019-10-13 14:47:10 -07:00
lib Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-10-12 14:46:14 -07:00
mm for-linus-20191010 2019-10-11 08:45:32 -07:00
net NFS Client Bugfixes for Linux 5.4-rc3 2019-10-11 14:28:59 -07:00
samples rpmsg updates for v5.4 2019-09-22 10:58:15 -07:00
scripts A few tracing fixes: 2019-10-13 14:47:10 -07:00
security selinux/stable-5.4 PR 20191007 2019-10-08 10:51:37 -07:00
sound sound fixes for 5.4-rc1 2019-09-24 16:46:16 -07:00
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-10-12 15:15:17 -07:00
usr kbuild: update compile-test header list for v5.4-rc2 2019-10-05 15:29:49 +09:00
virt KVM/arm fixes for 5.4, take #1 2019-10-03 12:08:50 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap MAINTAINERS: Use @kernel.org address for Paul Burton 2019-10-18 14:27:19 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: Use @kernel.org address for Paul Burton 2019-10-18 14:27:19 -07:00
Makefile Linux 5.4-rc3 2019-10-13 16:37:36 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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.