From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: file-backed guest memory Date: Thu, 12 Apr 2007 18:38:46 +0300 Message-ID: <461E5286.7090100@qumranet.com> References: <461E5181.6010504@mr511.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel To: Michael Riepe Return-path: In-Reply-To: <461E5181.6010504-0QoEqw4nQxo@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Michael Riepe wrote: > Hi! > > This is just a (probably silly) idea I had the other day. Currently, the > guest's memory is allocated inside the kernel and exported to userspace > via mmap(). But wouldn't it also be possible to create a file in > userspace and pass its descriptor to kvm? If we also pass file offset > and length parameters for each memslot, all segments can (but need not) > reside in the same file. There would be a persistent snapshot of the > VM's physical memory, and it would enable the VM to page out the guest's > pages. One could also do strange things like mapping a portion of the > file several times, e.g. to emulate an architecture with incomplete > address decoding. Applications that absolutely want to use anonymous > memory could pass -1 as the fd, as they do with mmap(MAP_ANONYMOUS). > Arnd suggested this way back when kvm was first posted on lkml, and I agree that this is a very useful mechanism. You get on-demand loading, swap, hugetlbfs, and maybe other nifty stuff. I think I know how to do this for the current mmu, but I'm worried that it will have a performance impact with the nested page tables mmu. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV