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

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Date:	Sun, 10 Aug 2008 09:40:37 +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 Sat, Aug 09, 2008 at 10:59:40AM -0700, Suresh Siddha wrote:
>
> 0. CPU's TS flag is set
> 
> 1. kernel using FPU in some optimized copy  routine and while doing
> kernel_fpu_begin() takes an interrupt just before doing clts()
> 
> 2. Takes an interrupt and ipsec uses padlock instruction. And we
> take a DNA fault as TS flag is still set.

Right, we could've fixed this by doing the clts before checking
TS_USEDFPU in kernel_fpu_begin.  However, I admit that taking a
fault in the general case for the PadLock is stupid anyway so we
should definitely fix this in the ways that you suggested.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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