From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dor Laor Subject: Re: [PATCH] fix reading from character devices Date: Mon, 21 Jan 2008 12:43:18 +0200 Message-ID: <1200912198.3188.6.camel@localhost.localdomain> References: <47946610.9040001@siemens.com> <47947045.6040106@qumranet.com> Reply-To: dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Jan Kiszka To: Avi Kivity Return-path: In-Reply-To: <47947045.6040106-atKUWr5tajBWk0Htik3J/w@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 On Mon, 2008-01-21 at 12:13 +0200, Avi Kivity wrote: > Jan Kiszka wrote: > > Hi Avi, > > > > commit "kvm: qemu: consume all pending I/O in I/O loop" > > (8ab8bb09f1115b9bf733f885cc92b6c63d83f420) broke reading data bursts > > from serial devices (and maybe from other character devices as well) by > > guests. Reason: serial devices do input flow control via fd_read_poll, > > but qemu now ignores this fact by pushing all data into the virtual > > device as soon as it is available. > > > > Patch below is not really nice (just as the whole internal virtual I/O > > interface at the moment, IMHO), but it re-enables the serial ports for > > now. > > > > > > I'm worried that it will break Dor's hack that speeds up virtio. Dor? > It should be fine. Tap device without my hack has fd_read_poll null and I hacked it to have a handler that returns false if virtio is used and true otherwise. So Jan's patch should set 'more' to 1 and it will be like before. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/