libvirt users - Mar 2015 - Re: machine='pc-q35-2.1' and sata controller

On Thu, 12 Mar 2015 14:56:08 -0400 Laine Stump <laine@laine.org> wrote:
> Here is the info straight from the author (I've also Cc'ed him to
this
> mail):
> 
> ==============> The AHCI migration series is here:
> 
> http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg05200.html
> These are all just tests, at any rate -- the actual patch that enables
> the migration is small and trivial and can be applied directly to
> current upstream:
> 
> http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg05202.html
> 
> All of the requisites that make AHCI safe to migrate are already
> upstream now.
> ==========> 
> As I understand it, all except the last patch will be in qemu 2.3. Also,
> he is actively soliciting people to test it, so if you've been wanting
> to learn how to build qemu from source, now is your opportunity to
> figure it out!
Are the needed patches in 2.3.0-rc0?
Is it possible to backport AHCI migration to RHEL 7.1 qemu or will it be too
much work?

Regards,
Nerijus

On 03/22/2015 08:23 PM, Nerijus Baliunas wrote:
> On Thu, 12 Mar 2015 14:56:08 -0400 Laine Stump <laine@laine.org>
wrote:
>
>> Here is the info straight from the author (I've also Cc'ed him
to this
>> mail):
>>
>> ==============>> The AHCI migration series is here:
>>
>> http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg05200.html
>
>> These are all just tests, at any rate -- the actual patch that enables
>> the migration is small and trivial and can be applied directly to
>> current upstream:
>>
>> http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg05202.html
>>
>> All of the requisites that make AHCI safe to migrate are already
>> upstream now.
>> ==========>>
>> As I understand it, all except the last patch will be in qemu 2.3.
Also,
>> he is actively soliciting people to test it, so if you've been
wanting
>> to learn how to build qemu from source, now is your opportunity to
>> figure it out!
>
> Are the needed patches in 2.3.0-rc0?
> Is it possible to backport AHCI migration to RHEL 7.1 qemu or will it be
too much work?
>
> Regards,
> Nerijus
>
The patches that improve the stability of AHCI migration are in 2.3-rc0. 
We still have not /enabled/ migration upstream, but editing to code to 
allow it is fairly trivial -- it's just a true/false value in the code.

My words of caution:

(1) We still have some bugs in the AHCI device which may necessitate 
changing the migration format of the device. Since we have not 
officially enabled migration, these format changes may leave you unable 
to migrate to later versions, because we are not currently being careful 
to maintain backwards compatibility with this "unreleased" device.

[If you are wondering what the probability of being unable to migrate to 
an official build where AHCI migration is supported is: Nearly 100%.]

(2) Because we have not enabled migration of AHCI officially, [And this 
is not enabled or supported in RHEL!] you may run into bugs. I wouldn't 
do this on a production system.

That said, if you do want to try it out on non-essential systems; for 
testing, development &c: I'd appreciate any bug reports.

See http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg05202.html 
as mentioned above for the patch that simply enables migration.

--js

On Mon, 23 Mar 2015 10:36:33 -0400 John Snow <jsnow@redhat.com> wrote:
> > Are the needed patches in 2.3.0-rc0?
> > Is it possible to backport AHCI migration to RHEL 7.1 qemu or will it
be too much work?
> 
> The patches that improve the stability of AHCI migration are in 2.3-rc0. 
> We still have not /enabled/ migration upstream, but editing to code to 
> allow it is fairly trivial -- it's just a true/false value in the code.
I built 2.3.0-rc0 but also added RH patches which applied (mainly for
pc-q35-rhel7.1.0 machine type support) from
http://ftp.redhat.com/pub/redhat/linux/enterprise/7Server/en/RHEV/SRPMS/qemu-kvm-rhev-2.1.2-23.el7_1.1.src.rpm

After suspending and restoring VM prints the following and hangs:

[root localhost ~]# [ 43.595571 irq 23: nobody cared (try booting with the
"irqpoll" option)
[ 43.596004] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.17.3-200.fc20.x86_64 #1
[ 43.596004] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009) . BIOS
seabios-1.7.5-8.el7 04/01/2014
[ 43.596004] 0000000000000000 be8ae26f5ae0021d ffff88007fc03d18 ffffffff81728acc
[ 43.596004] ffff88007a88a800 ffff88O07fc03d40 ffffffff810ea4e2_

Any idea why? I will try with a pure qemu w/o RH patches later.

Regards,
Nerijus