x86: Handle idle=nomwait cmdline properly for x86_idle
authorWyes Karny <wyes.karny@amd.com>
Mon, 6 Jun 2022 18:03:34 +0000 (23:33 +0530)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 17 Aug 2022 12:23:00 +0000 (14:23 +0200)
commit932b5e65245c7ac33373fdddd9c369688d39d20c
tree9f02b037aa96c06ff14572392285338ede1007eb
parent9ccb5d391c51fa99772c8defb53f0794200e2767
x86: Handle idle=nomwait cmdline properly for x86_idle

[ Upstream commit 8bcedb4ce04750e1ccc9a6b6433387f6a9166a56 ]

When kernel is booted with idle=nomwait do not use MWAIT as the
default idle state.

If the user boots the kernel with idle=nomwait, it is a clear
direction to not use mwait as the default idle state.
However, the current code does not take this into consideration
while selecting the default idle state on x86.

Fix it by checking for the idle=nomwait boot option in
prefer_mwait_c1_over_halt().

Also update the documentation around idle=nomwait appropriately.

[ dhansen: tweak commit message ]

Signed-off-by: Wyes Karny <wyes.karny@amd.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Tested-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lkml.kernel.org/r/fdc2dc2d0a1bc21c2f53d989ea2d2ee3ccbc0dbe.1654538381.git-series.wyes.karny@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Documentation/admin-guide/pm/cpuidle.rst
arch/x86/kernel/process.c