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

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Date:	Fri, 08 Aug 2008 20:30:49 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Wolfgang Walter <wolfgang.walter@...m.de>
CC:	Herbert Xu <herbert@...dor.apana.org.au>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	"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,
	vegard.nossum@...il.com
Subject: Re: Kernel oops with 2.6.26, padlock and ipsec: probably problem
 with fpu state changes

Wolfgang Walter wrote:
> 
> These FPU changes are already in 2.6.26. Undoing them, would that be accepted 
> for 2.6.26 stable?
> 
> Maybe the following solution would be possible: if a processor with padlock is 
> detected the memory for xstate is always allocated when the thread is created 
> instead "lazy"?
> 

That will effectively happen, so it doesn't really matter.

The true optimization would be to recognize that the state doesn't have 
to be saved, and track when we did so, and so on and so forth.

VIA really did their customers a disservice tying this to CR0.TS.

	-hpa
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