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From: Ingo Molnar <mingo@elte.hu>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Hugh Dickins <hugh@veritas.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Andi Kleen <ak@suse.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: preempt bug in set_pmd_pfn?
Date: Thu, 6 Mar 2008 13:52:15 +0100	[thread overview]
Message-ID: <20080306125215.GD20173@elte.hu> (raw)
In-Reply-To: <47CEF20D.5070608@goop.org>


* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> It seems to me that the correct fix is to just make __set_fixmap 
> disable preemption for its duration; it probably doesn't make much 
> difference for the native case, and it makes Xen happy.

actually, i think the correct approach is to remove the TLB flushing and 
perhaps to check that the old pte is not present. Do we ever _change_ 
mappings via __set_fixmap()? I think we only ever install them.

but if we ever change them somewhere then the correct approach is to do 
a flush_tlb_all(). It's not just about preemption but about the fact 
that we modified the kernel address space and we must propagate that to 
all CPUs.

the vmalloc() backtrace you sent - how did set_pte_pfn() get into that 
codepath - vmalloc shouldnt be using __set_fixmap().

	Ingo

  parent reply	other threads:[~2008-03-06 12:52 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-04 21:13 Jeremy Fitzhardinge
2008-03-04 21:28 ` Ingo Molnar
2008-03-04 21:27   ` Jeremy Fitzhardinge
2008-03-05  6:48     ` Ingo Molnar
2008-03-05 14:29       ` Hugh Dickins
2008-03-05 16:48         ` Jeremy Fitzhardinge
2008-03-05 17:38           ` Hugh Dickins
2008-03-05 19:18             ` Jeremy Fitzhardinge
2008-03-05 20:40               ` Hugh Dickins
2008-03-06 12:52               ` Ingo Molnar [this message]
2008-03-06 18:19                 ` Jeremy Fitzhardinge
2008-03-05 16:45       ` Jeremy Fitzhardinge
2008-03-05  0:06 ` Andi Kleen
2008-03-05  0:07   ` Jeremy Fitzhardinge
2008-03-05  0:16     ` Andi Kleen
2008-03-05  0:19       ` Jeremy Fitzhardinge
2008-03-05  1:28         ` Andi Kleen

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