netdev - Re: Kernel oops with 2.6.26, padlock and ipsec: probably problem with fpu state changes

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Message-ID: <489DC05E.2080901@zytor.com>
Date:	Sat, 09 Aug 2008 09:05:50 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
CC:	Suresh Siddha <suresh.b.siddha@...el.com>,
	Wolfgang Walter <wolfgang.walter@...m.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	"viro@...IV.linux.org.uk" <viro@...IV.linux.org.uk>,
	"vegard.nossum@...il.com" <vegard.nossum@...il.com>
Subject: Re: Kernel oops with 2.6.26, padlock and ipsec: probably problem
 with fpu state changes

Herbert Xu wrote:
> On Fri, Aug 08, 2008 at 04:11:21PM -0700, Suresh Siddha wrote:
>> With out the recent dynamic fpu allocation changes, while we don't see oops,
>> there is a possible race still present in older kernels(for example,
>> while kernel is using kernel_fpu_begin() in some optimized clear/copy
>> page and an interrupt/softirq happens which uses these padlock
>> instructions generating DNA fault).
> 
> No this wasn't a problem because kernel_fpu_begin clears TS and
> therefore we don't get faults on SSE instructions.
> 
> However, with your patch it will become a problem due to the
> fact that it wasn't designed to be nested.
> 

We're invoking this code from interrupt handlers?

	-hpa

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