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From: Avi Kivity on 29 Nov 2009 05:50
On 11/27/2009 11:56 PM, Nix wrote:
> So I installed my first KVM guest image (a prerelease of Ubuntu 9.10
> that I had lying around) this morning (through virt-manager, as it
> happens). Everything worked fine, the install was searingly fast
> compared to the UML virtual machines I'm used to.
>
> I got back to it this evening, restarted the VM, and found that it had
> suddenly slowed right down again, with one CPU being saturated with work
> even when nothing was happening. Looking at the syslog shows (what would
> be but for ratelimit) incredible numbers of these messages being logged:
>
> Nov 27 21:44:00 spindle info: [444857.792205] device vnet0 entered promiscuous mode
> Nov 27 21:44:00 spindle info: [444857.794347] linux-net: port 2(vnet0) entering learning state
> Nov 27 21:44:03 spindle warning: [444860.856640] __ratelimit: 928705 callbacks suppressed
> Nov 27 21:44:03 spindle err: [444860.856729] emulation failed (pagetable) rip 7f3845f36a7b 66 0f 7f 07
>

66 0f 7f 07 movdqa %xmm0,(%rdi)

which we don't emulate.

Can you, using the qemu monitor, see where the guest is trying to write?

(qemu) info registers
(qemu) x/30i $eip - 20


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error compiling committee.c: too many arguments to function

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From: Avi Kivity on 30 Nov 2009 03:20
On 11/30/2009 01:31 AM, Nix wrote:
> On 29 Nov 2009, Avi Kivity stated:
>
>> Most likely, either this or something similar is called on a userspace
>> device driver. Can you check if this is triggered by starting X?
>>
> *sigh* I just wasted twenty minutes trying to find some way, *any* way
> to not start X under Ubuntu Karmic, so as to test this. None is evident.
> I can't even figure out what and where in upstart's horrific dependency
> tangle is starting X in the first place: deleting suspicious-looking
> things from rc*.d has no effect at all. I can't even tell if rc*.d is
> still used, nor if the concept of runlevel is even meaningful any
> longer. There are lots of things googleable that claim to say how to do
> this, but all relate to the non-dependency-based inittab-emulating
> method used in previous Ubuntu versions.
>
> Anyone know?
>

At least on Fedora, you you can change the runlevel in /etc/inittab (the
sole remaining function of the file).

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Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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From: Avi Kivity on 1 Dec 2009 05:00
On 11/30/2009 11:40 PM, Nix wrote:
>
> 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?
>

'sendkey alt-ctrl-f2' from the qemu monitor.

So it looks like it is X related, and we'll have no choice other than to
emulate the instruction. Annoying, since we don't emulate sse
instructions yet.

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error compiling committee.c: too many arguments to function

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From: Avi Kivity on 1 Dec 2009 05:20
On 12/01/2009 11:59 AM, Avi Kivity wrote:
>
> So it looks like it is X related, and we'll have no choice other than
> to emulate the instruction. Annoying, since we don't emulate sse
> instructions yet.
>

I reproduced it and confirmed - the instruction is accessing 0xa0000,
the low memory vga window.

Is Ubuntu not testing on kvm? It's their default hypervisor after all.


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error compiling committee.c: too many arguments to function

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