From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: Re: dom0 serial input overruns Date: Thu, 24 Mar 2011 07:54:54 -0400 Message-ID: <20110324115454.GB23293@dumpdata.com> References: <87zkoq6onj.fsf@tac.ki.iif.hu> <20110320204321.GE3948@dumpdata.com> <87oc54a0zc.fsf@tac.ki.iif.hu> <20110322152710.GA27284@dumpdata.com> <87k4fqiz9y.fsf@tac.ki.iif.hu> <878vw54qd7.fsf@tac.ki.iif.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <878vw54qd7.fsf@tac.ki.iif.hu> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ferenc Wagner Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Wed, Mar 23, 2011 at 07:57:08PM +0100, Ferenc Wagner wrote: > Ferenc Wagner writes: > > > Konrad Rzeszutek Wilk writes: > > > >> wferi writes: > >> > >>> the Xen (and Linux) serial console is also lossy as hell [...] > >>> However, this lossage isn't accompanied by any warning. > >> > >> Oooh, strange. > > > > I have to take this back, partly. Although the bare linux serial console > > is *much* more reliable (I couldn't trigger much visible corruption by a > > simple 'while echo " X"; do :; done' loop, as under > > Xen, even that heavily loses characters during the bootup message storm > > when going through the Serial-over-LAN thingie. Now I took that out of > > the picture entirely, using a physical serial connection instead. This > > made a world of difference: bootup logs are pretty much perfect now, and > > even the above while loop seldom produces a single wiggle (57600 baud). > > See http://apt.niif.hu/xen_bootup.log for good example (the stray > > character before "Allocated console ring" seems fully deterministic). > > I'll test the same console setup under bare Linux tomorrow, maybe that > > won't make a single error... > > Yes, testing confirms that bare Linux is even better, I couldn't notice > a single missing character (vs. some glitch in every couple of seconds > under Xen). > > > Still, these (infrequent) glitches over hvc0 go unnoticed by the system, > > as far as I can tell. > > Who should notice this, after all? hvc0 itself probably not, being a > virtual device. Does the Xen serial driver detect overruns? It is not a serial driver anymore. It uses some other type of API that does not have all of the fancy serial support. No idea actually how it does flow control. > > >> Look for a thread from 'M A Young' about keyboard issues. > > > > Long thread, I'll read through it tomorrow. > > There's a good chance I'm running without the fix mentioned in the > conclusion (I'm yet to check), and my serial interrupts really hit CPU0 > alone. But my serial connection mostly works, not totally dead like in > that thread. That is good. Happy to have been able to fix your problem by just talking about it! BTW, haven't looked in details at the logs - little swamped right now. > -- > Thanks, > Feri. > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel