linux-kernel - Re: [BUG 4.2-rc8] Interrupt occurs while apply

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Message-ID: <alpine.DEB.2.11.1509041536120.15006@nanos>
Date:	Fri, 4 Sep 2015 15:37:24 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Borislav Petkov <bp@...en8.de>
cc:	"Richard W.M. Jones" <rjones@...hat.com>,
	Chuck Ebbert <cebbert.lkml@...il.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is
 patching the handler

On Fri, 4 Sep 2015, Borislav Petkov wrote:
> On Thu, Sep 03, 2015 at 12:41:47PM +0200, Thomas Gleixner wrote:
> > Nah. I rather put the local_irq_save into optimize_nops(). All other
> > callers of add_nops() are operating on a buffer and use text_poke
> > after that. Aside of that optimize_nops() is missing a sync_core().
> 
> Whoops.
> 
> > Updated patch below.
> 
> Looks good, thanks.
> 
> Hrrm, maybe optimize_nops() should work on a buffer and do
> text_poke_early() too at the end, so that it doesn't differ from all the
> other paths changing kernel text. So as to stuff like that doesn't get
> missed next time I'm touching it.
> 
> But with your way we don't need the additional buffer. I guess your
> solution is better resource-wise.

I pondered the buffer/text_poke variant, but that's too much of a
hassle for a fix supposed to go to stable.

Resourcewise you could use the buffer which is available in
apply_alternatives anyway.

Thanks,

	tglx
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