From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Jan Beulich <JBeulich@novell.com>
Cc: Xiaowei Yang <xiaowei.yang@huawei.com>,
Nick Piggin <npiggin@kernel.dk>,
fanhenglong@huawei.com, Kaushik Barde <kbarde@huawei.com>,
Kenneth Lee <liguozhu@huawei.com>,
linqaingmin <linqiangmin@huawei.com>,
wangzhenguo@huawei.com, Wu Fengguang <fengguang.wu@intel.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
linux-kernel@vger.kernel.org
Subject: Re: One (possible) x86 get_user_pages bug
Date: Thu, 27 Jan 2011 17:25:02 +0100 [thread overview]
Message-ID: <1296145502.15234.235.camel@laptop> (raw)
In-Reply-To: <4D41A651020000780002ED36@vpn.id2.novell.com>
On Thu, 2011-01-27 at 16:07 +0000, Jan Beulich wrote:
>
> Nick, based on your doing of the initial implementation, would
> you be able to estimate whether disabling get_user_pages_fast()
> altogether for Xen would be performing measurably worse than
> adding the locks (but continuing to avoid acquiring mm->mmap_sem)
> as suggested by Xiaowei? That's of course only if the latter is correct
> at all, of which I haven't fully convinced myself yet.
Adding the lock will result in deadlocks, __get_user_pages_fast() is
used from NMI context.
Then again, I've got no clue if Xen even has NMIs..
next prev parent reply other threads:[~2011-01-27 16:24 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-27 13:05 One (possible) x86 get_user_pages bug Xiaowei Yang
2011-01-27 13:56 ` Peter Zijlstra
2011-01-27 14:30 ` Jan Beulich
2011-01-28 10:51 ` Peter Zijlstra
2011-01-27 14:49 ` Jan Beulich
2011-01-27 14:49 ` Jan Beulich
2011-01-27 15:01 ` Peter Zijlstra
2011-01-27 18:27 ` Jeremy Fitzhardinge
2011-01-27 18:27 ` Jeremy Fitzhardinge
2011-01-27 19:27 ` Peter Zijlstra
2011-01-30 13:01 ` Avi Kivity
2011-01-30 22:21 ` Kaushik Barde
2011-01-30 22:21 ` Kaushik Barde
2011-01-31 18:04 ` Jeremy Fitzhardinge
2011-01-31 20:10 ` Kaushik Barde
2011-01-31 20:10 ` Kaushik Barde
2011-01-31 22:10 ` Jeremy Fitzhardinge
2011-01-27 16:07 ` Jan Beulich
2011-01-27 16:07 ` Jan Beulich
2011-01-27 16:25 ` Peter Zijlstra [this message]
2011-01-27 16:41 ` Jan Beulich
2011-01-27 16:41 ` Jan Beulich
2011-01-27 16:56 ` Peter Zijlstra
2011-01-27 21:24 ` Nick Piggin
2011-01-28 7:17 ` Xiaowei Yang
2011-01-28 7:17 ` Xiaowei Yang
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