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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: Avi Kivity <avi@xxxxxxxxxx>
Date: Sun, 30 Jan 2011 15:01:45 +0200
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, Wu Fengguang <fengguang.wu@xxxxxxxxx>, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
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On 01/27/2011 08:27 PM, Jeremy Fitzhardinge wrote:
And even just considering virtualization, having non-IPI-based tlb
shootdown is a measurable performance win, since a hypervisor can
optimise away a cross-VCPU shootdown if it knows no physical TLB
contains the target VCPU's entries.  I can imagine the KVM folks could
get some benefit from that as well.

It's nice to avoid the IPI (and waking up a cpu if it happens to be asleep) but I think the risk of deviating too much from the baremetal arch is too large, as demonstrated by this bug.

(well, async page faults is a counterexample, I wonder if/when it will bite us)

error compiling committee.c: too many arguments to function

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