From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v3 9/11] KVM: MMU: prefetch ptes when intercepted guest #PF Date: Thu, 01 Jul 2010 20:13:40 +0800 Message-ID: <4C2C8674.4080607@cn.fujitsu.com> References: <4C2AF9FA.9020601@cn.fujitsu.com> <4C2AFB65.2030807@cn.fujitsu.com> <20100630204324.GA5366@amt.cnet> <4C2BEB48.3080705@cn.fujitsu.com> <4C2C85E6.1050303@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM list To: Avi Kivity Return-path: In-Reply-To: <4C2C85E6.1050303@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Avi Kivity wrote: > On 07/01/2010 04:11 AM, Xiao Guangrong wrote: >> >> Marcelo Tosatti wrote: >> >> >>>> + >>>> + addr = gfn_to_hva_many(vcpu->kvm, gfn,&entry); >>>> + if (kvm_is_error_hva(addr)) >>>> + return -1; >>>> + >>>> + entry = min(entry, (int)(end - start)); >>>> + ret = __get_user_pages_fast(addr, entry, 1, pages); >>>> + if (ret<= 0) >>>> + return -1; >>>> >>> Why can't you use gfn_to_pfn_atomic() here, one page at a time? Is >>> the overhead significant that this is worthwhile? >>> >>> You're bypassing the centralized interface. >>> >> I think it's worthwhile to do since we can reduce gup overhead, no reason >> to traverse process's page table again and again for the consecutive >> pages. >> > > Then we should make the centralized interface work in terms of multiple > pages, and write the single-page interfaces in terms of the multipage > interfaces. > Umm, i'll import a new function named gfn_to_pfn_many_atomic(... int *enough), using 'enough' to indicate whether have got the all consecutive pages in the slot, Marcelo, how about it? :-)