[libvirt] [PATCH] send default USB controller in xml to destination during migration on PPC64

[Cole Robinson]

On 04/28/2016 03:05 AM, Shivaprasad bhat wrote:
> Thanks Cole.. Here is the XML for a PPC64 guest.
> https://paste.fedoraproject.org/360574/61826548/ 
> You can see the slot 1 is free as I unplugged a device there.
> 
> On X86, Q35 seems to use the model ich9-ehci1 by default. So, may not be
> applicable there. 
> For pc-i440fx, I couldn't force USB to occupy any place other than slot 1
> function 2. So, might not be applicable there too. 
> 

Thanks for the info. Sounds like we can make the check be !ARCH_IS_X86 then,
since 0.9.4 didn't really have actively developed support for anything that
isn't x86.

Can you send a v2 with that change, and add a comment above the check about
what the original purpose was (libvirt <= 0.9.4 migration compat) and that it
doesn't apply to non-x86 arch and in fact can cause issues with ppc64

Thanks,
Cole

> Regards,
> Shiva
> 
> On Wed, Apr 27, 2016 at 9:27 PM, Cole Robinson <crobinso at redhat.com
> <mailto:crobinso at redhat.com>> wrote:
> 
>     On 03/02/2016 10:09 AM, Shivaprasad G Bhat wrote:
>     > The default USB controller is not sent to destination as the older versions
>     > of libvirt(0.9.4 or earlier as I see in commit log of 409b5f54) didn't
>     > support them. For some archs where the support started much later can
>     > safely send the USB controllers without this worry. For now, changing the
>     > checks to allow PPC64 here. If we can track the historical support for
>     > other archs, the changes can be extrapolated to them too.
>     >
>     > The patch fixes a bug that, if the USB controller happens to occupy
>     > a slot after disks/interfaces and one of them is hot-unplugged, then
>     > the default USB controller added on destination takes the smallest slot
>     > number and that would lead to savestate mismatch and migration
>     > failure.
>     >
>     > Signed-off-by: Shivaprasad G Bhat <sbhat at linux.vnet.ibm.com
>     <mailto:sbhat at linux.vnet.ibm.com>>
>     > ---
>     >  src/qemu/qemu_domain.c |    2 +-
>     >  1 file changed, 1 insertion(+), 1 deletion(-)
>     >
>     > diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
>     > index 9044792..6ecc0e2 100644
>     > --- a/src/qemu/qemu_domain.c
>     > +++ b/src/qemu/qemu_domain.c
>     > @@ -2226,7 +2226,7 @@ qemuDomainDefFormatBuf(virQEMUDriverPtr driver,
>     >                  usb = def->controllers[i];
>     >              }
>     >          }
>     > -        if (usb && usb->idx == 0 && usb->model == -1) {
>     > +        if (!ARCH_IS_PPC64(def->os.arch) && usb && usb->idx == 0 &&
>     usb->model == -1) {
>     >              VIR_DEBUG("Removing default USB controller from domain '%s'"
>     >                        " for migration compatibility", def->name);
>     >              toremove++;
>     >
> 
>     Sorry this didn't receive a timely response. Can you provide the XML config
>     that reproduces this? I wonder if this is something that affects x86 too. And
>     if so we may want to fix it in a different way
> 
>     Thanks,
>     Cole
> 
>