linux-kernel - Re: perf hw in kexeced kernel broken in tip

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Message-ID: <20101208190158.GA8565@redhat.com>
Date:	Wed, 8 Dec 2010 14:01:58 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Vivek Goyal <vgoyal@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Jason Wessel <jason.wessel@...driver.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Haren Myneni <hbabu@...ibm.com>
Subject: Re: perf hw  in kexeced kernel broken in tip

On Wed, Dec 08, 2010 at 10:43:14AM -0800, Yinghai Lu wrote:
> 
> can you add sth force_... in command line to take over ownership of perf from BIOS or previous kernel ?
> 
> then still can use perf etc after we kexec from RHEL or SLES kernel to later kernel ( from 2.6.37)

My understand is that you can't because the BIOS is actively using it
behind the scenes of the kernel (well during an SMI).  I have a machine
where I tried to force take it but it still stopped triggering interrupts.

Cheers,
Don
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