From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH/RFC 0/2] CPU hotplug virtio driver Date: Wed, 09 Jan 2008 12:42:22 +0200 Message-ID: <4784A50E.6050302@qumranet.com> References: <11998740663306-git-send-email-gcosta@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, marcelot-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Glauber de Oliveira Costa Return-path: In-Reply-To: <11998740663306-git-send-email-gcosta-H+wXaHxf7aLQT0dZR+AlfA@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 Glauber de Oliveira Costa wrote: > I'm sending a first draft of my proposed cpu hotplug driver for kvm/virtio > The first patch is the kernel module, while the second, the userspace pci device. > > The host boots with the maximum cpus it should ever use, through the -smp parameter. > Due to real machine constraints (which qemu copies), i386 does not allow for any addition > of cpus after boot, so this is the most general way. > > I do however, include an "attempt_buffer" in the userspace part. It's purpose is to > allow tools like virt-manager to set a max_cpus (-smp), and a desired number of cpus > in their configuration files. (and AFAICT, there's is no easy way for them to tell when the > backend driver is up and running) > > Other than that, it should be pretty much straightforward. > > Looking forward for your comments > > I would much prefer to see cpu hotplug implemented via acpi. Such an implementation would work on older kernels without change, and will also work with other operating systems. It isn't a high-speed interface so virtio doesn't buy us anything. Linux appears to support it (CONFIG_ACPI_HOTPLUG_CPU) so all that's needed is the host side support (likely qemu/bios only). Of course hacking on acpi is fun, if you're the kind of person than enjoys dental surgery. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace