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Wyes Karny 6e9d12125f cpufreq: amd-pstate: Fix invalid write to MSR_AMD_CPPC_REQ 
`amd_pstate_set_epp` function uses `cppc_req_cached` and `epp` variable
to update the MSR_AMD_CPPC_REQ register for AMD MSR systems. The recent
commit 7cca9a9851 ("cpufreq: amd-pstate: avoid uninitialized variable
use") changed the sequence of updating cppc_req_cached and writing the
MSR_AMD_CPPC_REQ. Therefore while switching from powersave to
performance governor and vice-versa in active mode MSR_AMD_CPPC_REQ is
set with the previous cached value. To fix this: first update the
`cppc_req_cached` variable and then call `amd_pstate_set_epp` function.

 - Before commit 7cca9a9851 ("cpufreq: amd-pstate: avoid uninitialized
   variable use"):

With powersave governor:
[    1.652743] amd_pstate_epp_init: writing to cppc_req_cached = 0x1eff
[    1.652744] amd_pstate_set_epp: writing cppc_req_cached = 0x1eff
[    1.652746] amd_pstate_set_epp: writing min_perf = 30, des_perf = 0, max_perf = 255, epp = 0

Changing to performance governor:
[  300.493842] amd_pstate_epp_init: writing to cppc_req_cached = 0xffff
[  300.493846] amd_pstate_set_epp: writing cppc_req_cached = 0xffff
[  300.493847] amd_pstate_set_epp: writing min_perf = 255, des_perf = 0, max_perf = 255, epp = 0

 - After commit 7cca9a9851 ("cpufreq: amd-pstate: avoid uninitialized
   variable use"):

With powersave governor:
[    1.646037] amd_pstate_set_epp: writing cppc_req_cached = 0xffff
[    1.646038] amd_pstate_set_epp: writing min_perf = 255, des_perf = 0, max_perf = 255, epp = 0
[    1.646042] amd_pstate_epp_init: writing to cppc_req_cached = 0x1eff

Changing to performance governor:
[  687.117401] amd_pstate_set_epp: writing cppc_req_cached = 0x1eff
[  687.117405] amd_pstate_set_epp: writing min_perf = 30, des_perf = 0, max_perf = 255, epp = 0
[  687.117419] amd_pstate_epp_init: writing to cppc_req_cached = 0xffff

 - After this fix:

With powersave governor:
[    2.525717] amd_pstate_epp_init: writing to cppc_req_cached = 0x1eff
[    2.525720] amd_pstate_set_epp: writing cppc_req_cached = 0x1eff
[    2.525722] amd_pstate_set_epp: writing min_perf = 30, des_perf = 0, max_perf = 255, epp = 0

Changing to performance governor:
[ 3440.152468] amd_pstate_epp_init: writing to cppc_req_cached = 0xffff
[ 3440.152473] amd_pstate_set_epp: writing cppc_req_cached = 0xffff
[ 3440.152474] amd_pstate_set_epp: writing min_perf = 255, des_perf = 0, max_perf = 255, epp = 0

Fixes: 7cca9a9851 ("cpufreq: amd-pstate: avoid uninitialized variable use")
Signed-off-by: Wyes Karny <wyes.karny@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
History 2023-02-15 15:58:07 +01:00
arch Merge back cpufreq material for 6.3-rc1. 2023-02-14 15:22:31 +01:00
block block-6.2-2023-02-03 2023-02-03 11:35:42 -08:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-01-31 17:53:01 +09:00
crypto This update includes the following changes: 2022-12-14 12:31:09 -08:00
Documentation Cpufreq arm updates for 6.3 2023-02-14 15:25:07 +01:00
drivers cpufreq: amd-pstate: Fix invalid write to MSR_AMD_CPPC_REQ 2023-02-15 15:58:07 +01:00
fs for-6.2-rc7-tag 2023-02-12 11:26:36 -08:00
include Merge back cpufreq material for 6.3-rc1. 2023-02-14 15:22:31 +01:00
init Kbuild fixes for v6.2 (3rd) 2023-01-21 10:56:37 -08:00
io_uring io_uring: always prep_async for drain requests 2023-01-27 06:29:29 -07:00
ipc Non-MM patches for 6.2-rc1. 2022-12-12 17:28:58 -08:00
kernel tracing: Fix showing of TASK_COMM_LEN instead of its value 2023-02-12 13:52:17 -08:00
lib - Lock the proper critical section when dealing with perf event context 2023-02-05 11:03:56 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm Fix page corruption caused by racy check in __free_pages 2023-02-12 10:30:05 -08:00
net rds: rds_rm_zerocopy_callback() use list_first_entry() 2023-02-09 10:37:26 +01:00
rust rust: print: avoid evaluating arguments in pr_* macros in unsafe blocks 2023-01-16 00:54:35 +01:00
samples ftrace: Export ftrace_free_filter() to modules 2023-01-24 11:20:58 -05:00
scripts Kbuild fixes for v6.2 (4th) 2023-02-04 11:30:23 -08:00
security tomoyo: Update website link 2023-01-13 23:11:38 +09:00
sound sound fixes for 6.2-rc8 2023-02-10 08:37:48 -08:00
tools Revert "mm: Always release pages to the buddy allocator in memblock_free_late()." 2023-02-11 10:51:45 -08:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt VFIO fixes for v6.2-rc6 2023-01-23 11:56:07 -08:00
.clang-format iommufd for 6.2 2022-12-14 09:15:43 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore *.rpm 2022-12-30 17:22:14 +09:00
.mailmap 25 hotfixes, mainly for MM. 13 are cc:stable. 2023-02-03 10:01:57 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: update SCTP maintainers 2023-02-02 11:35:33 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: Add myself as maintainer for arch/sh (SUPERH) 2023-02-12 13:57:09 -08:00
Makefile Linux 6.2-rc8 2023-02-12 14:10:17 -08:00
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.