From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Daniel P. Berrange" Subject: Re: [PATCH] [QEMU-DM] Upgrade emulated UART to 16550A. Date: Wed, 5 Dec 2007 14:24:46 +0000 Message-ID: <20071205142446.GA12556@redhat.com> References: <515922b50712040832ifc112b1j52e1d2390d7c7459@mail.gmail.com> Reply-To: "Daniel P. Berrange" Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <515922b50712040832ifc112b1j52e1d2390d7c7459@mail.gmail.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Trolle Selander Cc: xen-devel List-Id: xen-devel@lists.xenproject.org On Tue, Dec 04, 2007 at 05:32:39PM +0100, Trolle Selander wrote: > This patch adds 16550 emulation to qemu-dm. I still consider it a work in > progress, but from my testing, it consistently performs better than the old > code already, sometimes considerably so (on my laptop, dumping out data over > serial from a HVM DomU -> pty in Dom0 was up to 5.3 times faster than with > the old 16450 code). I can consistenly reach full 115200 baud speeds over > physical serial lines when the virtual device is backed by a phys port, > which I never could with the old code. > > There are still some things to be done. I want to add proper error handling, > so that overflow/framing & parity errors on the physical port get detected > and reported by the virtual port. Also, now that FIFOs are in place, I > believe performance could be improved significantly by putting some code > into the hypervisor so that reads & writes from the FIFOs don't have to exit > into qemu-dm at all. I'm also reading up on the specs for newer uarts with > deeper FIFOs. > > However, for now, I think this patch is already quite good, and I don't > think I should sit on it any longer. I'm looking forward to hearing what > results others will get with it. >>From a quick glance through the patches there doesn't appear to be anything that is Xen specific in these patches. If I am correct in this understanding, could you send the patches to upstream qemu-devel mailing lists, so Xen does not have to carry this fork forever. Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|