From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754859Ab1BUOwM (ORCPT ); Mon, 21 Feb 2011 09:52:12 -0500 Received: from www.tglx.de ([62.245.132.106]:40936 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753209Ab1BUOwL (ORCPT ); Mon, 21 Feb 2011 09:52:11 -0500 Date: Mon, 21 Feb 2011 15:51:56 +0100 (CET) From: Thomas Gleixner To: KY Srinivasan cc: "gregkh@suse.de" , "linux-kernel@vger.kernel.org" , "devel@linuxdriverproject.org" , "virtualization@lists.osdl.org" , Haiyang Zhang , Hank Janssen Subject: RE: [PATCH]: Staging: hv: Allocate the vmbus irq dynamically In-Reply-To: <6E21E5352C11B742B20C142EB499E048013C67@TK5EX14MBXC128.redmond.corp.microsoft.com> Message-ID: References: <1297799735-25917-1-git-send-email-kys@microsoft.com> <6E21E5352C11B742B20C142EB499E048011738@TK5EX14MBXC124.redmond.corp.microsoft.com> <6E21E5352C11B742B20C142EB499E048011787@TK5EX14MBXC124.redmond.corp.microsoft.com> <6E21E5352C11B742B20C142EB499E04801191C@TK5EX14MBXC124.redmond.corp.microsoft.com> <6E21E5352C11B742B20C142EB499E048013C67@TK5EX14MBXC128.redmond.corp.microsoft.com> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 21 Feb 2011, KY Srinivasan wrote: > > > > There are various ways to solve that proper. > > > > > > > > - You can provide the interrupt number from ACPI/PCI or whatever your HV > > > > provides as enumeration. > > > > > > > > - Use a fixed vector like XEN does for the event channel > > > > > > > > - Use dynamic allocation in the IOAPIC space like the kernel does for > > > > MSI(-X) > > > > > > > > Thanks, > > > > > > > > tglx > > > > > > I am not claiming that what I have done here is the best possible solution. > > > However, I will submit to you that it is better than what we had here > > > prior to this patch. I will address this and a whole lot of other issues > > > in future patches. > > > > No, it's _NOT_ better in any way. You trade breaking your PV thing > > against breaking random other drivers. Care to explain why you think > > that's better ? > > The root device for the VM is bound to the PV driver on some distributions. > So, if we cannot load the PV drivers, we do not have a system that boots. > In general, the system performance without these PV drivers is so poor that > for all practical purposes, having the PV drivers is almost a requirement > for having a useable system. While the platform supports configuration of the VM with > some emulated devices, it is not a recommended configuration (because of > performance reasons) for Linux virtual machines on the Hyper-V platform. It does not matter whether it's recommended or not. If it results in a non usable emulated device it's broken. Just imagine you grab the serial interrupt, which results in not having a debug console. Not at all acceptable. > I have spent significantly more time debating this patch than > developing this patch that I still think improves the current > driver. I will leave it to Greg and other powers that be to decide > if this patch will be accepted. Let me know what your verdict is. As I said, any other clean solution (and I pointed out 3) over this hack. Thanks, tglx