Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758271Ab3DSJkY (ORCPT ); Fri, 19 Apr 2013 05:40:24 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:60964 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756008Ab3DSJkX (ORCPT ); Fri, 19 Apr 2013 05:40:23 -0400 Date: Fri, 19 Apr 2013 10:39:53 +0100 From: Will Deacon To: Pranavkumar Sawargaonkar Cc: Peter Maydell , "linaro-kernel@lists.linaro.org" , Patch Tracking , Marc Zyngier , "linux-kernel@vger.kernel.org" , "kvmarm@lists.cs.columbia.edu" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [RFC] arm64: Early printk support for virtio-mmio console devices. Message-ID: <20130419093953.GD13283@mudshark.cambridge.arm.com> References: <1366264344-28025-1-git-send-email-pranavkumar@linaro.org> <20130419090558.GA13283@mudshark.cambridge.arm.com> <20130419092752.GB13283@mudshark.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1672 Lines: 34 On Fri, Apr 19, 2013 at 10:34:56AM +0100, Pranavkumar Sawargaonkar wrote: > On 19 April 2013 15:00, Peter Maydell wrote: > > On 19 April 2013 10:27, Will Deacon wrote: > >> On Fri, Apr 19, 2013 at 10:25:35AM +0100, Pranavkumar Sawargaonkar wrote: > >>> I am not against using 8250 emulation (as far as it solves printk > >>> issues for kernel booting logs), but my point is why not to add early > >>> read-write support for virtio console, which also can be useful in > >>> emulation less mach-virt environment also ? > >> > >> We can have both, but only one of those requires a change to the virtio > >> specification. > > > > I don't think avoiding writing a spec is necessarily a good reason > > for insisting on emulation of a lump of hardware 95% of whose > > capabilities you aren't going to use... > > True. > Also 8250 will require emulation of registers, and i am not sure about > if mach-virt will have any emulation of real hw ? The point of mach-virt is that it is completely parameterised. So, if you're not emulating an 8250, then don't tell the kernel that you have one! Similarly, if you *do* emulate it, then either create a device-tree node for it or pass the appropriate earlyprintk= string on the command line. As far as kvmtool is concerned, we'd probably have a new command-line option for arm64, allowing you to specify the early console device. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/