[PATCH 1/1] NEWS.rst: update with pSeries initial memory fix

Daniel P. Berrangé berrange at redhat.com
Wed Jan 6 15:03:46 UTC 2021


On Wed, Jan 06, 2021 at 12:00:30PM -0300, Daniel Henrique Barboza wrote:
> 
> 
> On 1/6/21 11:47 AM, Daniel P. Berrangé wrote:
> > On Wed, Jan 06, 2021 at 11:42:09AM -0300, Daniel Henrique Barboza wrote:
> > > Commit v6.10.0-103-g198c1eb6b4 fixed this issue.
> > > 
> > > Signed-off-by: Daniel Henrique Barboza <danielhb413 at gmail.com>
> > > ---
> > > 
> > > I forgot to update NEWS.rst back then :/
> > > 
> > >   NEWS.rst | 7 +++++++
> > >   1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/NEWS.rst b/NEWS.rst
> > > index da88b19d0a..2c5cee77db 100644
> > > --- a/NEWS.rst
> > > +++ b/NEWS.rst
> > > @@ -23,6 +23,13 @@ v7.0.0 (unreleased)
> > >   * **Bug fixes**
> > > +  * Avoid taking extra host memory when launching pSeries guests
> > > +
> > > +    Under certain conditions, pSeries guests were being launched with more
> > > +    RAM than it was specified in the domain XML by the user. New pSeries
> > > +    domains created with libvirt 7.0.0 will always launch with the right
> > > +    amount of initial memory.
> > 
> > Surely this is going to break live migration from old to new libvirt,
> > as the QEMU started in the dest host will have a smaller -m arg.
> 
> This bug fix is being effective just when VIR_DOMAIN_DEF_PARSE_ABI_UPDATE is set.
> The migration code doesn't set this flag.

That doesn't make it safe.

virDomainCreateXML on the source Libvirt 7.0.0 on the source  will set
PARSE_ABI_UPDATE and thus set the new smaller RAM size.

Now we live migrate to libvirt 6.9.0 on dest host, and that will not
set PARSE_ABI_UPDATE and thus set the larger RAM size.

QEMU will fail to load the migration stream since the source and dest
RAM sizes differ.

Regards,
Daniel
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