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Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor device
From: |
Jamie Lokier |
Subject: |
Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2) |
Date: |
Tue, 14 Apr 2009 19:19:08 +0100 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Avi Kivity wrote:
> Daniel P. Berrange wrote:
> >Yes indeed its a little crazy :-) As anthony mentioned if libvirt were
> >able to be notified of changes a user makes in the monitor, there's no
> >reason we could not allow end users to access the monitor of a VM
> >libvirt is managing. We just need to make sure libvirt doesn't miss
> >changes like attaching or detaching block devices, etc, because that'll
> >cause crash/data loss later when libvirt migrates or does save/restore,
> >etc because it'll launch QEMU with wrong args
> >
>
> You still have an inherent race here.
>
> user: plug in disk
> libvirt: start migration, still without disk
> qemu: libvirt, a disk has been plugged in.
Then fix it. The race is not necessary.
user: plug in a disk
libvirt: lock VM against user changes incompatible with migration
qemu: libvirt, lock granted
libvirt: query for current disk state
libvirt: start migration, knows about the disk
The "libvirt, a disk has been plugged in" will be delivered but it's
not important. libvirt queries the state of things after it acquires
the lock and before it starts migration.
> That means that to debug a problem in the field you have to locate a
> guest's host, and follow it around as it migrates (or disable migration).
That's right you do. Is there any way to debug a guest without
disabling migration? I don't think there is at present, so of course
you have to disable migration when you debug. Another reason for that
"lock against migration" mentioned above.
-- Jamie
- Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), (continued)
- Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Anthony Liguori, 2009/04/11
- Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Avi Kivity, 2009/04/11
- Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Jamie Lokier, 2009/04/12
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Daniel P. Berrange, 2009/04/14
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Avi Kivity, 2009/04/14
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Daniel P. Berrange, 2009/04/14
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Jan Kiszka, 2009/04/14
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Avi Kivity, 2009/04/14
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Avi Kivity, 2009/04/14
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Jamie Lokier, 2009/04/14
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2),
Jamie Lokier <=
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Avi Kivity, 2009/04/16
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Zachary Amsden, 2009/04/11
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Zachary Amsden, 2009/04/12
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Gerd Hoffmann, 2009/04/14
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Jamie Lokier, 2009/04/14
- Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Avi Kivity, 2009/04/11
- Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Andreas Färber, 2009/04/11
- Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Jamie Lokier, 2009/04/12
- Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Jamie Lokier, 2009/04/09
- Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2), Gerd Hoffmann, 2009/04/09