From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 1/1 v2] KVM: MMU: Optimize guest page table walk Date: Tue, 26 Apr 2011 17:54:24 +0300 Message-ID: <4DB6DCA0.1000303@redhat.com> References: <20110422003222.9d08aee3.takuya.yoshikawa@gmail.com> <20110422003444.5b3a876a.takuya.yoshikawa@gmail.com> <4DB52B1B.5080407@web.de> <20110425173215.740417ae.yoshikawa.takuya@oss.ntt.co.jp> <4DB53BA8.60401@web.de> <20110426135035.5f569397.yoshikawa.takuya@oss.ntt.co.jp> <4DB66791.50403@web.de> <20110426234034.ab2ed524.takuya.yoshikawa@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Jan Kiszka , Takuya Yoshikawa , mtosatti@redhat.com, kvm@vger.kernel.org, xiaoguangrong@cn.fujitsu.com, Joerg.Roedel@amd.com To: Takuya Yoshikawa Return-path: Received: from mx1.redhat.com ([209.132.183.28]:60309 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755490Ab1DZOyh (ORCPT ); Tue, 26 Apr 2011 10:54:37 -0400 In-Reply-To: <20110426234034.ab2ed524.takuya.yoshikawa@gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: On 04/26/2011 05:40 PM, Takuya Yoshikawa wrote: > On Tue, 26 Apr 2011 08:34:57 +0200 > Jan Kiszka wrote: > > > > Google said that there was a similar talk on LKML in 2004. > > > > > > On that threads, Linus explained how to tackle on the 64-bit get_user > > > implementation. But I could not see what happened after that. > > > > Mmh, maybe the kernel was lacking a real use case, so no one seriously > > cared. > > > > I don't see a fundamental blocker for an x86-32 __get_user_8 version > > based on two mov. I would give it a try. > > > > Jan > > > > Thank you! > > Avi, do we revert the patch now, or ...? Please post a simple patch that uses two get_user()s for that case (64-bit pte on 32-bit host). Then work with the x86 tree to see if they'll accept 64-bit get_user(), and once they do, we can go back to a simple get_user() again. btw, I think we can use __get_user() here since the address must have been already validated. -- error compiling committee.c: too many arguments to function