From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC] KVM MMU: thinking of shadow page cache Date: Thu, 01 Apr 2010 12:12:05 +0300 Message-ID: <4BB46365.7020400@redhat.com> References: <4BB15B1A.7090901@cn.fujitsu.com> <4BB1FD69.6040409@redhat.com> <4BB461E7.9000109@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Ingo Molnar , Marcelo Tosatti , Sheng Yang , KVM list , LKML To: Xiao Guangrong Return-path: In-Reply-To: <4BB461E7.9000109@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 04/01/2010 12:05 PM, Xiao Guangrong wrote: > >> We've considered this in the past, it makes sense. The big question is >> whether any guests actually map the same page table through PDEs with >> different permissions (mapping the same page table through multiple PDEs >> is very common, but always with the same permissions). Do you know of >> any such guest? >> > I also don't know whether have such guest. > Maybe my idea is no good for current OS, thanks for your comments. > In fact there are plans to make kvm such a guest (when running in nested mode) - when we perform live migration we write-protect all guest pages, and it's reasonable to use the top-level shadow page to write protect all memory at once instead of iterating over all mmu pages. When that goes in, we should also implement your idea. -- error compiling committee.c: too many arguments to function