linux-kernel - 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 11:05:21 +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 12:37:24PM -0700, Suresh Siddha wrote:
> On Sat, Aug 09, 2008 at 11:52:24AM -0700, Siddha, Suresh B wrote:
> > Backing out lazy allocation is not just enough here. Let me think a little
> > more on this.
> 
> Can we have something like irq_ts_save() and irq_ts_restore(), which will
> do something like:
> 
> int irq_ts_save()
> {
> 	if (!in_interrupt())
> 		return 0;
> 
> 	if (read_cr0() & X86_CR0_TS) {
> 		clts();
> 		return 1;
> 	}
> 	return 0;
> }
> 
> void irq_ts_restore(int TS_state)
> {
> 	if (!in_interrupt())
> 		return 0;

This check isn't necessary.

> 
> 	if (TS_state)
> 		stts();
> }

But yes this scheme looks good to me.

> kernel_fpu_begin:
> 	...
> 
> 	local_irq_disable();
> 
>         if (me->status & TS_USEDFPU)
>                 __save_init_fpu(me->task);
>         else
>                 clts(); 
> 
> 	local_irq_enable();
> 	...

Couldn't we just move clts before the USEDFPU check? That huld
close the window.

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