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[Xen-devel] Re: One (possible) x86 get_user_pages bug

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: [Xen-devel] Re: One (possible) x86 get_user_pages bug
From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Date: Thu, 27 Jan 2011 20:27:56 +0100
Cc: Kaushik Barde <kbarde@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Kenneth Lee <liguozhu@xxxxxxxxxx>, Nick Piggin <npiggin@xxxxxxxxx>, Marcelo Tosatti <mtosatti@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Jan Beulich <JBeulich@xxxxxxxxxx>, wangzhenguo@xxxxxxxxxx, Xiaowei Yang <xiaowei.yang@xxxxxxxxxx>, linqaingmin <linqiangmin@xxxxxxxxxx>, fanhenglong@xxxxxxxxxx, Avi, Wu Fengguang <fengguang.wu@xxxxxxxxx>, Kivity <avi@xxxxxxxxxx>
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On Thu, 2011-01-27 at 10:27 -0800, Jeremy Fitzhardinge wrote:
> So is there some way we can preserve the current scheme's benefits while
> making it a bit more general?  (If anyone else has non-IPI-based
> shootdown, it would be s390; is there some inspiration there?  An
> instruction perhaps?) 

Well, you can provide a xen gupf implementation based on rcu freed
page-tables like powerpc, sparc and s390 have.

But you'll have to change the mmu_gather implementation of xen and use
the get_page_unless_zero() thing mentioned before (or use

But I see no need to change the x86 implementation, if the architecture
ever changes the way it does tlb invalidation we need to change more
than just the gupf implementation.

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