From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030567AbWK3Poi (ORCPT ); Thu, 30 Nov 2006 10:44:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030572AbWK3Poi (ORCPT ); Thu, 30 Nov 2006 10:44:38 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:14728 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1030567AbWK3Poh (ORCPT ); Thu, 30 Nov 2006 10:44:37 -0500 Date: Thu, 30 Nov 2006 16:44:25 +0100 From: Ingo Molnar To: Christoph Hellwig , Avi Kivity , kvm-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, akpm@osdl.org Subject: Re: [PATCH 1/38] KVM: Create kvm-intel.ko module Message-ID: <20061130154425.GB28507@elte.hu> References: <456AD5C6.1090406@qumranet.com> <20061127121136.DC69A25015E@cleopatra.q> <20061127123606.GA11825@elte.hu> <20061130142435.GA13372@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061130142435.GA13372@infradead.org> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -4.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-4.5 required=5.9 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] 1.4 AWL AWL: From: address is in the auto white-list Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Christoph Hellwig wrote: > > please move this from drivers/kvm/ to kernel/kvm/ [or even into a > > toplevel kvm/ directory] - KVM is not a "driver", KVM enhances the > > core Linux kernel with hypervisor functionality. > > Actually it's exactly a driver. It's a character driver that exposes > the virtualization features of modern x86 hardware. [...] you are fundamentally wrong. In the end KVM is a fundamental and complex infrastructure that enables Linux to provide full hardware capabilities to another OS via the resources of this OS. This concept justifies a system call and a place in linux/kernel/. It's not fundamentally limited to x86 either. Full virtualization (and paravirtualization) makes sense on any platform. And there's no reason KVM be limited to full virtualization alone - both paravirtualization and accelerated guest drivers need a sane hypercall API. > [...] Pretty similar to things like the msr or mtrr driver that expose > cpu features as character drivers aswell. you can expose everything as character drivers and ioctls, but that doesnt make it the right solution. It might /start out/ as a driver, because that's an easy to hack model, but the moment something becomes important enough (and virtualization certainly is such a model) it demands a system call. Just like inotify started out as an ioctl hack, but then was (rightfully) moved to the system-call space. [ Which btw. was on your request ;-) ] Ingo