Re: [Qemu-devel] [PATCH 11/18] migration: introduce capability localhost

[Lei Li]

On 08/21/2013 11:08 PM, Eric Blake wrote:
> On 08/21/2013 01:18 AM, Lei Li wrote:
> > Introduce migration capability localhost.
> >
> > Signed-off-by: Lei Li <address@hidden>
> > ---
> >   include/migration/migration.h |    3 +++
> >   migration.c                   |   12 ++++++++++++
> >   qapi-schema.json              |    8 +++++++-
> >   3 files changed, 22 insertions(+), 1 deletions(-)
> >
> > +++ b/qapi-schema.json
> > @@ -629,10 +629,16 @@
> >   # @auto-converge: If enabled, QEMU will automatically throttle down the guest
> >   #          to speed up convergence of RAM migration. (since 1.6)
> >   #
> > +# @localhost: If enabled, QEMU will support localhost migration. This feature
> > +#             allows live upgrade of a running QEMU instance by doing localhost
> > +#             migration with page flipping. It requires the source and 
> > destination
> > +#             are both on localhost. Disabled by default. (since 1.7)
> Logically, ALL new migration parameters should be disabled by default,
> as that provides the sanest back-compat setting.  Your last sentence is
> therefore redundant.  But this is certainly a much nicer implementation
> than your v1 attempt.
>
> If I understand correctly, attempts to use 'local:...' are rejected
> unless you first use migrate-set-capabilities to turn on localhost
> migration support.

Hi Eric,

The attempt to use 'local' will not be rejected if we don't use
migrate-set-capabilities first. Because the destination QEMU process
have no idea whether this capability is set in MigrationState. It will
just lead to a failure of migration connection.

According to Paolo's new suggestion in patch set 17/18, IIUIC, it will get
rid of this 'local' prefix, just use 'unix' protocol URI. In this case,
the incoming part for localhost migration will only be called if the
source support it by checking if the pipe can be got via SCM_RIGHTS.
 

>


--
Lei