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

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Message-ID: <20080809143727.GA30499@gondor.apana.org.au>
Date:	Sat, 9 Aug 2008 22:37:27 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	"H. Peter Anvin" <hpa@...or.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

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.

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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