From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: Xen 4 serial hangs during boot Date: Fri, 20 Jul 2012 20:25:39 +0100 Message-ID: <5009B0B3.8080004@citrix.com> References: <4E95EBD6.7010400@theshore.net> <20111013104654.GB44937@ocelot.phlegethon.org> <500999DD.1010708@theshore.net> <50099A2F.9030907@citrix.com> <50099C62.20802@theshore.net> <50099DF8.7090800@citrix.com> <5009AD29.3060401@theshore.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5009AD29.3060401@theshore.net> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: "Christopher S. Aker" Cc: xen devel List-Id: xen-devel@lists.xenproject.org On 20/07/12 20:10, Christopher S. Aker wrote: > On 7/20/12 2:05 PM, Andrew Cooper wrote: >> Alternatively, use `xl debug-keys` > Interesting. 'xl debug-keys h' got me ~1448 bytes onto the serial > console, except it is old buffered output from exactly where it left off > during boot. 1448 bytes is about the size of 'h' output from another > working box. The same thing happened with 'm'. Xen is flushing an > equal amount of characters from the buffer as generated by debug-key > command output. > > I can continue to poke the buffer until I see output from things I've > issued, however it still refuses to respond to serial input > (control-aaa) nor can I get dom0 to echo chars. It's currently running > a * dump which has been going now for over an hour, currently on vcpu > 435628. I won't be doing that again. > > Any lightblubs going off? Not especially. It sounds like the serial ring buffer filled up and never got drained. How easy is this to reproduce for you? In the past, I have had success debugging Xen like this with an outb(0x3f8, ) in certain locations. Perhaps the serial_rx interrupt handler, or failing that, do_irq checking for vector 0xf0. That should allow you to see whether Xen is actually receiving interrupts when you try to send characters. > > -Chris -- Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer T: +44 (0)1223 225 900, http://www.citrix.com