Re: [Qemu-devel] qemu-kvm guest which won't 'cont' (emulation failure?)

[Kevin Wolf]

Am 24.10.2011 12:58, schrieb Chris Webb:
> Kevin Wolf <address@hidden> writes:
> 
>> Am 24.10.2011 12:00, schrieb Chris Webb:
>>> I have qemu monitor access and can even strace the relevant qemu process if
>>> necessary: is it possible to use this to diagnose what's caused this guest
>>> to stop, e.g. the unsupported instruction if it's an emulation failure?
>>
>> Another common cause for stopped VMs are I/O errors, for example writes
>> to a sparse image when the disk is full.
> 
> This guest are backed by LVM LVs so I don't think they can return EFULL, but I
> could imagine read errors, so I've just done a trivial test to make sure I can
> read them end-to-end:
> 
>   0015# dd 
> if=/dev/mapper/guest\:e549f8e1-4c0e-4dea-826a-e4b877282c07\:ide\:0\:0 
> of=/dev/null bs=1M
>   3136+0 records in
>   3136+0 records out
>   3288334336 bytes (3.3 GB) copied, 20.898 s, 157 MB/s
> 
>   0015# dd 
> if=/dev/mapper/guest\:e549f8e1-4c0e-4dea-826a-e4b877282c07\:ide\:0\:1 
> of=/dev/null bs=1M
>   276+0 records in
>   276+0 records out
>   289406976 bytes (289 MB) copied, 1.85218 s, 156 MB/s
> 
> Is there any way to ask qemu why a guest has stopped, so I can distinguish IO
> problems from emulation problems from anything else?

In qemu 1.0 we'll have an extended 'info status' that includes the stop
reason, but 0.14 doesn't have this yet (was committed to git master only
recently).

If you attach a QMP monitor (see QMP/README, don't forget to send the
capabilities command, it's part of creating the connection) you will
receive messages for I/O errors, though.

Kevin