From: Peter Zijlstra <peterz@infradead.org>
To: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
tim.c.chen@linux.intel.com, Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH] x86: Don't use MWAIT if explicitly requested
Date: Fri, 18 Oct 2019 09:12:06 +0200 [thread overview]
Message-ID: <20191018071206.GZ2328@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1571370354-17736-1-git-send-email-zhenzhong.duan@oracle.com>
On Fri, Oct 18, 2019 at 11:45:54AM +0800, Zhenzhong Duan wrote:
> If 'idle=nomwait' is specified or process matching what's in
> processor_idle_dmi_table, we should't use MWAIT at bootup stage before
> cpuidle driver loaded, even if it's preferred by default on Intel.
>
> Add a check so that HALT instruction is used in those cases.
The comment in idle_setup():
/*
* If the boot option of "idle=nomwait" is added,
* it means that mwait will be disabled for CPU C2/C3
* states. In such case it won't touch the variable
* of boot_option_idle_override.
*/
boot_option_idle_override = IDLE_NOMWAIT;
explicitly states this option is for C2+
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> ---
> arch/x86/kernel/process.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index 5e94c43..37fc577 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -667,6 +667,10 @@ static void amd_e400_idle(void)
> */
> static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
> {
> + /* Don't use MWAIT-C1 if explicitly requested */
> + if (boot_option_idle_override == IDLE_NOMWAIT)
> + return 0;
And this is very much about C1...
OTOH, "idle=halt" should be forcing HLT over MWAIT, so did you want to
write:
if (boot_option_idle_override == IDLE_HALT)
return 0;
instead?
next prev parent reply other threads:[~2019-10-18 7:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-18 3:45 [PATCH] x86: Don't use MWAIT if explicitly requested Zhenzhong Duan
2019-10-18 7:12 ` Peter Zijlstra [this message]
2019-10-18 8:47 ` Zhenzhong Duan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191018071206.GZ2328@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=boris.ostrovsky@oracle.com \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=tglx@linutronix.de \
--cc=tim.c.chen@linux.intel.com \
--cc=x86@kernel.org \
--cc=zhenzhong.duan@oracle.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).