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Re: [Xen-devel] General protection fault in netback

2012/2/15 Pasi Kärkkäinen <pasik@xxxxxx>:

AS>> Unfortunately, I'm not skilled at compiling the kernel myself.
AS>> I tried building the newest 3.2.6 with all Xen options enabled,
AS>> but the resulting system didn't have netback.ko module at all,
AS>> barely booted, and xm was not able to communicate with VMM.

PK> About compiling the dom0 kernel, see this wiki page:
PK> http://wiki.xen.org/wiki/XenParavirtOps#Configure_kernel_for_dom0_support

Thanks, it looks like I just messed some "y" with "m" and vice versa
("m" is presented as a meaningless bullet in GUI). By the way, that how-to
contains dubious lines for CONFIG_XEN_DEV_EVTCHN and CONFIG_XEN_GNTDEV.

Well, now the system boots more eagerly, although the kernel still
seems to be slightly incompatible with distro's environment and my hardware.
But at least xend is now responding and is able to run DomUs as usual.

I started and stopped all the swarm of VMs several times (without letting them
to run for some time), and observed no GPF. But instead of this I get
screen garbling: while a DomU is starting or stopping, the whole graphical
desktop is sometimes painted with either black or not-so-random garbage,
and even mouse pointer can become garbled; I have to move / resize windows
to get them repainted. Network connectivity between Dom0 and [subsequently
started] DomUs does not break though.

On one hand, I am not sure whether the video driver is not to be
blamed for glitches,
because graphics already does not work as usual: it is not hardware-accelerated
with my custom kernel (while it is with stock kernel), and the screen is garbled
on Xorg startup, before login promt is displayed. On the other hand, this is not
in any way normal, as Xen operations must not interfere with Dom0's desktop
(or was it direct VRAM corruption?).

This happens even when "suspicious" domains (NetBSD with CARP) are not
started: on a freshly booted Dom0, just having 4 essential DomUs is enough
to get that screen garbling when shutting down 1 or 2 of them for the
first time.

But when I return to stock kernel, I can run a dozen of such DomUs (including
those NetBSD load-balancers), starting and stopping them many times
without a problem. Recently, no GPF occurred when only 1 out of 2 balancers
is started, or none of them started at all; or it just needs much more uptime
to accumulate memory corruption for a GPF.

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