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David Woodhouse 474bd0b82e KVM/x86: Reduce retpoline performance impact in slot_handle_level_range(), by always inlining iterator helper methods 
commit 928a4c3948 upstream.

With retpoline, tight loops of "call this function for every XXX" are
very much pessimised by taking a prediction miss *every* time. This one
is by far the biggest contributor to the guest launch time with retpoline.

By marking the iterator slot_handle_…() functions always_inline, we can
ensure that the indirect function call can be optimised away into a
direct call and it actually generates slightly smaller code because
some of the other conditionals can get optimised away too.

Performance is now pretty close to what we see with nospectre_v2 on
the command line.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Tested-by: Filippo Sironi <sironi@amazon.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Filippo Sironi <sironi@amazon.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: arjan.van.de.ven@intel.com
Cc: dave.hansen@intel.com
Cc: jmattson@google.com
Cc: karahmed@amazon.de
Cc: kvm@vger.kernel.org
Cc: rkrcmar@redhat.com
Link: http://lkml.kernel.org/r/1518305967-31356-4-git-send-email-dwmw@amazon.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2018-02-22 15:42:20 +01:00
arch
block blk-mq: quiesce queue before freeing queue 2018-02-16 20:23:09 +01:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto crypto: hash - prevent using keyed hashes without setting key 2018-02-16 20:23:00 +01:00
Documentation arm: spear13xx: Fix dmas cells 2018-02-22 15:42:18 +01:00
drivers crypto: sun4i_ss_prng - convert lock to _bh in sun4i_ss_prng_generate 2018-02-22 15:42:19 +01:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs ocfs2: try a blocking lock before return AOP_TRUNCATED_PAGE 2018-02-22 15:42:16 +01:00
include compiler-gcc.h: __nostackprotector needs gcc-4.4 and up 2018-02-22 15:42:19 +01:00
init bpf: introduce BPF_JIT_ALWAYS_ON config 2018-01-31 14:03:49 +01:00
ipc License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kernel tracing: Prevent PROFILE_ALL_BRANCHES when FORTIFY_SOURCE=y 2018-02-22 15:42:13 +01:00
lib swiotlb: suppress warning when __GFP_NOWARN is set 2018-02-22 15:42:15 +01:00
mm Revert "defer call to mem_cgroup_sk_alloc()" 2018-02-13 10:19:48 +01:00
net dccp: CVE-2017-8824: use-after-free in DCCP code 2018-02-16 20:22:45 +01:00
samples samples/bpf: adjust rlimit RLIMIT_MEMLOCK for xdp1 2017-12-20 10:10:31 +01:00
scripts kasan: rework Kconfig settings 2018-02-16 20:23:04 +01:00
security ima/policy: fix parsing of fsuuid 2018-02-03 17:38:53 +01:00
sound ASoC: skl: Fix kernel warning due to zero NHTL entry 2018-02-16 20:23:04 +01:00
tools kselftest: fix OOM in memory compaction test 2018-02-22 15:42:15 +01:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: Handle CPU_PM_ENTER_FAILED 2018-02-16 20:23:03 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING [PATCH] update FSF address in COPYING 2005-09-10 10:06:29 -07:00
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS Merge branch 'akpm' (patches from Andrew) 2017-11-09 18:26:51 -08:00
Makefile Linux 4.14.20 2018-02-16 20:23:12 +01:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.