From mboxrd@z Thu Jan  1 00:00:00 1970
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: Running KVM version ?
Date: Thu, 9 Apr 2015 17:58:21 +0200
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Cc: kvm list <kvm@vger.kernel.org>
To: Florent B <florent@coppint.com>
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2015-04-09 15:27+0200, Florent B:
> Hi everyone,
> 
> This list seems to be a developer list, I didn't find any "users" list.

I don't think it exists, KVM is used mostly by programs and they are not
sophisticated enough to communicate.
(or they are, which is why humans aren't invited)

> So please forgive me if I'm at the wrong place.

qemu-discuss/libvirt-users/openstack-operators (whatever you face) or
stack overflow are better for questions about virtualization.

> I would like to know if there's a way to know the version of a running
> kvm process ?

I think you meant QEMU process.  KVM is the kernel part and it can't
change while any VM is running.  (`uname -r` gives kernel version.)

There are at least four ways to get VM's QEMU version.
I presume you are using at most libvirt.

1a) virsh
   1. get name of the VM
   2. # virsh qemu-monitor-command $name --hmp info version
1b) qemu monitor
   1. access the monitor (if you don't use libvirt, you should know how)
   2. (qemu) info version
   (2+. curse and repent if you set up JSON monitor)

3) reading /proc/$pid/mem
   1. get PID of the QEMU process
   2. # cd /proc/$pid/
   3. # offset=$((0x`awk -F - '/r-x.*qemu/{print $1}' maps`))
   4. # dd skip=$offset if=mem bs=1 | strings | grep 'emulator version'

4) gdb
   (You probably don't have debuginfo and the option above is easier.)

> I have some VMs running for 100+ days, and I would like to know if I
> need to restart them to run with a newer version of kvm.

No need to know the version for that.  You can take look when the binary
was updated and compare it with process start time.