From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber de Oliveira Costa Subject: Re: [PATCH/RFC] Implement the memory_map hypercall Date: Fri, 24 Nov 2006 12:57:34 -0200 Message-ID: <20061124145734.GE7171@redhat.com> References: <20061124140810.GC7171@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jun Koi Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Fri, Nov 24, 2006 at 11:36:36PM +0900, Jun Koi wrote: > Glauber, what is this hypercall for? To map hypervisor memory from Dom0? This hypercall (already declared, but currently always returning ENOSYS) is meant to give a guest (any guest) the idea on how should this physical memory mapping look like. Currently, linux guest kernels checks for the result of such a call, and stabilish a memory mapping on their own if it returns ENOSYS. However, such mapping is not proving itself to be the most suitable one, specially in a long term. That said, when you boot a 300mb guest, instead of: BIOS-provided physical RAM map: Xen: 0000000000000000 - 0000000013400000 (usable) You'd see your RAM mapping being extended to whatever value is set in d->memory_map_limit ( or even for some reason, in the future, a differently organized map) -- Glauber de Oliveira Costa Red Hat Inc. "Free as in Freedom"