From: Suresh Siddha <suresh.b.siddha@intel.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86: enable x2apic early at the first point
Date: Sat, 21 Feb 2009 15:33:01 -0800 [thread overview]
Message-ID: <20090221233300.GB6733@linux-os.sc.intel.com> (raw)
In-Reply-To: <49A083A2.30303@kernel.org>
On Sat, Feb 21, 2009 at 02:43:46PM -0800, Yinghai Lu wrote:
> for x2apic preenabled system,
> when nox2apic is used, cpu_has_x2apic will be cleared, apic will be xapic phys_flat or flat.
> is that expected?
>
> should
> 1. ignore nox2apic
> 2. or try to disable x2apic?
This scenario might be useful for debug purposes? But it might
not be simple/straight fwd in OS to implement this, as we need to do two things.
1. Go back to xapic mode using the state transition diagram in SDM.
2. And also, we need to disable the interrupt-remapping setup by the bios,
so that chipset and cpu's are in same mode.
If BIOS has enabled x2apic, it is for a reason (mostly platform
has more logical cpus and hence need x2apic to brinup all the AP's etc).
And typically other than very high end platforms, I don't expect bios
to turn on x2apic.
thanks,
suresh
next prev parent reply other threads:[~2009-02-21 23:33 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-19 21:50 [PATCH] x86: enable x2apic early at the first point Yinghai Lu
2009-02-19 22:13 ` Suresh Siddha
2009-02-19 22:42 ` Yinghai Lu
2009-02-19 23:28 ` Suresh Siddha
2009-02-20 8:35 ` Ingo Molnar
2009-02-20 9:09 ` Gleb Natapov
2009-02-20 9:41 ` Ingo Molnar
2009-02-20 10:58 ` Gleb Natapov
2009-02-20 11:06 ` Ingo Molnar
2009-02-20 11:06 ` Gleb Natapov
2009-02-20 12:33 ` Gleb Natapov
2009-02-20 12:59 ` Ingo Molnar
2009-02-20 9:51 ` Ingo Molnar
2009-02-20 9:55 ` Ingo Molnar
2009-02-21 22:23 ` Suresh Siddha
2009-02-21 22:43 ` Yinghai Lu
2009-02-21 23:33 ` Suresh Siddha [this message]
2009-02-22 17:21 ` Ingo Molnar
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=20090221233300.GB6733@linux-os.sc.intel.com \
--to=suresh.b.siddha@intel.com \
--cc=akpm@linux-foundation.org \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=tglx@linutronix.de \
--cc=yinghai@kernel.org \
/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