linux-kernel - Re: [PATCH -v3] x86: Disable x2apic if nox2apic is specified

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Message-Id: <1288331608.2717.14.camel@sbsiddha-MOBL3>
Date:	Thu, 28 Oct 2010 22:53:28 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v3] x86: Disable x2apic if nox2apic is specified

On Tue, 2010-10-26 at 23:27 -0700, Yinghai Lu wrote:
> For
> 1. x2apic preenabled system
> 2. first kernel have x2apic enabled, and try to kexec second kernel with "nox2apic"
> 
> Will put back cpu with apic id < 255 into xapic mode, instead of panic.
> 
> -v2: use x2apic_disabled instead of nox2apic, Suggested by Thomas
>      update x2apic_supported with x2apic_disabled, Suggested by Thomas
> 
> -v3: add checking for boot cpu apic id > 255. in that case will just panic
>      --- pointed out by Suresh.
> 

Can we please hold off in merging this patch for a bit? There are some
subtleties in going back to xapic when the platform/cpu's are in x2apic
mode. I will check and get back to you on this after KS.

thanks,
suresh

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