From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: help with understanding GPA/GVA issues Date: Fri, 10 Aug 2007 19:59:36 +0300 Message-ID: <46BC9978.3060801@qumranet.com> References: <1186718958.4866.15.camel@ghaskins-t60p.haskins.net> <46BC7709.4030807@codemonkey.ws> <1186756859.4866.31.camel@ghaskins-t60p.haskins.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Gregory Haskins Return-path: In-Reply-To: <1186756859.4866.31.camel-5CR4LY5GPkvLDviKLk5550HKjMygAv58XqFh9Ls21Oc@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 Gregory Haskins wrote: >>> >>> >> Yes, you can pass through any gva. There are couple of things to be >> aware of though. When passing a gva, you have to be sure that the gva >> is actually mapped in memory as KVM cannot cause Linux to fault in a >> page. >> > > Cool! Ya, I totally understand and agree that it has to be "DMA" class > memory that is mapped and pinned in guest context. IIUC you basically > need to follow the same rules as you would for a DMA based device in a > bare-metal scenario. > > Note that passing a virtual address is highly discouraged as its meaning can change from vcpu to vcpu, it might not be mapped, translation is slow, etc. Just let the guest do the translation. > On this topic: I know there has been talk going on of giving each VM > its own linux va context. IIUC, when that happens we wouldn't need the > gva_to_hpa type functions, right? We could use things like > copy_to_user(), etc? Out of curiosity, what's the status of that > project? > We have something running at qumranet, will be sent out soon. I am somewhat discouraged in trying to get the thing to page -- Shaohua's approach is much simpler. ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/