linux-kernel - Re: 2.6.31.5 x86-64 KVM: 'emulation failed (pagetable) rip 7fb49335da7b 66 0f 7f 07'

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Date:	Mon, 30 Nov 2009 21:40:46 +0000
From:	Nix <nix@...eri.org.uk>
To:	Alejandro Riveira Fernández 
	<ariveira@...il.com>
Cc:	Avi Kivity <avi@...hat.com>, kvm@...r.kernel.org,
	Linux-Kernel-Mailing-List <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.31.5 x86-64 KVM: 'emulation failed (pagetable) rip 7fb49335da7b 66 0f 7f 07'

On 30 Nov 2009, Alejandro Riveira Fernández spake thusly:
>  When I install the infamous nvidia driver I use. « sudo stop gdm » 
> there are a start and restart aliases too see « man initctl ».

Aha! That's done it. New upstartish aliases I hadn't noticed...

FWIW, my qemu startup line (later adjusted, see below):

DISPLAY=mutilate:0 /usr/bin/qemu-system-x86_64 -M pc-0.11 -enable-kvm -m 1024 \
    -smp 2 -name ubuntwo -vnc :0 -boot c \
    -drive file=/vm/linux/ubuntwo.img,if=virtio,index=0,boot=on,format=raw \
    -drive file=/usr/local/tmp/ubuntu-9.10-beta-alternate-amd64.iso,if=ide,media=cdrom,index=2 \
    -net nic,macaddr=52:54:00:4b:f7:7f,vlan=0,model=virtio,name=virtio.0 \
    -net tap,vlan=0,ifname=ubuntwo,script=/sbin/qemu-linux.ifup,downscript=/sbin/qemu-linux.ifdown \
    -parallel none -usb -k en-gb -vga vmware -soundhw ac97 -runas linux-vm \
    -serial mon:telnet::10404,server,nowait

> Sometimes is not enough though and I have to stop gdm and then pkill
> the X server

Unfortunately stopping X renders the vnc console useless. I got the SDL
console working (note for frustrated others: a quick 'xhost +blah' no
longer works in recent X versions, xhost support is gone from the
server: you must propagate your xauth cookie across instead), whereupon
it coredumps on me with a pretty-much-useless stacktrace:

vmsvga_fifo_run (s=0x117e5e8) at /usr/src/qemu/x86_64-spindle/hw/vmware_vga.c:572
572     /usr/src/qemu/x86_64-spindle/hw/vmware_vga.c: No such file or directory.
        in /usr/src/qemu/x86_64-spindle/hw/vmware_vga.c
(gdb) bt
#0  vmsvga_fifo_run (s=0x117e5e8) at /usr/src/qemu/x86_64-spindle/hw/vmware_vga.c:572
#1  0x0000000000000000 in ?? ()

I seem to be getting a lot of coredumps from qemu right now :(

So I started with -vga std. The emulation failed flood is unaffected
(strangely it's not consistent: it happens about half the time). As soon
as I issue a 'stop gdm', X exits and the emulation flood halts: but
although there are other getties running I can't find a way to switch to
them, as qemu has stolen Ctrl-Alt for its own purposes: so the system is
pretty much useless (maybe I should get an sshd up and try to restart
things from there). (I've never needed to do this before: either my
qemus have been text mode all the time, or X with one console.)

Surely switching VTs is possible: any clues?

Unfortunately Ubuntu bug 417859 has broken the recovery console so I
can't use that to get me in in text mode and *then* start X. Not fixed,
but then it's only a bug in something critical to system recovery which
has been open for months and has had variations on the same bug open for
*two flipping years*. Sheesh.

:/
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