This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] segfault in VM

To: James Harper <JamesH@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] segfault in VM
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 22 Jul 2004 03:56:26 +0100
Cc: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxxx
Delivery-date: Thu, 22 Jul 2004 03:58:09 +0100
Envelope-to: steven.hand@xxxxxxxxxxxx
In-reply-to: Your message of "Thu, 22 Jul 2004 12:48:06 +1000." <C86E359D-E456-4BE1-BF77-2D72688B95F8@mimectl>
List-archive: <http://sourceforge.net/mailarchive/forum.php?forum=xen-devel>
List-help: <mailto:xen-devel-request@lists.sourceforge.net?subject=help>
List-id: List for Xen developers <xen-devel.lists.sourceforge.net>
List-post: <mailto:xen-devel@lists.sourceforge.net>
List-subscribe: <https://lists.sourceforge.net/lists/listinfo/xen-devel>, <mailto:xen-devel-request@lists.sourceforge.net?subject=subscribe>
List-unsubscribe: <https://lists.sourceforge.net/lists/listinfo/xen-devel>, <mailto:xen-devel-request@lists.sourceforge.net?subject=unsubscribe>
Sender: xen-devel-admin@xxxxxxxxxxxxxxxxxxxxx
> As a first test I have just disabled networking via nics=0 in the config, and 
> running this script in dom1:
> #!/bin/sh
> while [ 1 = 1 ]
> do
>   dd if=/dev/sda1 of=/dev/null bs=1024 count=128K &
>   dd if=/dev/sda1 of=/dev/null bs=1024 skip=256K count=256K
> done
> it tells me 'ioctl 801c6d02 not supported by XL blkif' but that doesn't seem 
> to matter. Anyway, there are no crashes so far so i'm thinking at this stage 
> that the block interface stuff is probably fine and I should now concentrate 
> on the network. Disabling the block stuff will be a huge hassle at this stage 
> so i'll have to let it go for the moment.

It does seem more likely that the network backend driver is to blame
-- it's considerably more complicated than the blkdev driver.

> I think i need a crash course in how all this hangs together before I can 
> understand what i'm testing... My understanding is as follows:
> packets sent to dom0.vif1.0 appear at dom1.eth0.
> packets sent to dom1.eth0 appear at dom0.vif1.0.

Yes, it's basically a point-to-point link. The transmit side on each
interface is directly linked to the receive side on the other.

> and that's about it. Are they symmetrical? Is the transmit code for 
> dom0.vif1.0 the same as the transmit code for dom1.eth0? Ditto for receive?

No. dom1.eth0 is implemented by the frontend driver
dom0.vif* is implemented by arch/xen/drivers/netif/backend/main.c 

So they look symmetric to users, but the implementation is not

 -- Keir

This SF.Net email is sponsored by BEA Weblogic Workshop
FREE Java Enterprise J2EE developer tools!
Get your free copy of BEA WebLogic Workshop 8.1 today.
Xen-devel mailing list