Re: [Xen-devel] [PATCH 2/2] xl: add target cpupool parameter to xl migrate

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Oct 02, 2018 at 05:08:27PM +0200, Juergen Gross wrote:
> On 02/10/2018 16:42, Andrew Cooper wrote:
> > On 02/10/18 15:19, Juergen Gross wrote:
> >> Add an option to specify the cpupool on the target machine when doing
> >> a migration of a domain. Currently a domain is always migrated to the
> >> cpupool with the same name as on the source machine.
> >>
> >> Specifying "-c <cpupool>" will migrate the domain to the specified
> >> cpupool on the target machine. Specifying an empty string for <cpupool>
> >> will use the default cpupool (normally "Pool-0") on the target machine.
> >>
> >> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> >> ---
> >>  docs/man/xl.pod.1.in      |  5 +++++
> >>  tools/xl/xl.h             |  1 +
> >>  tools/xl/xl_cmdtable.c    |  3 +++
> >>  tools/xl/xl_migrate.c     | 15 ++++++++++-----
> >>  tools/xl/xl_saverestore.c | 10 +++++++++-
> >>  5 files changed, 28 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/docs/man/xl.pod.1.in b/docs/man/xl.pod.1.in
> >> index b74764dcd3..62f7c0f039 100644
> >> --- a/docs/man/xl.pod.1.in
> >> +++ b/docs/man/xl.pod.1.in
> >> @@ -451,6 +451,11 @@ domain. See the corresponding option of the I<create> 
> >> subcommand.
> >>  Send the specified <config> file instead of the file used on creation of 
> >> the
> >>  domain.
> >>  
> >> +=item B<-c> I<cpupool>
> >> +
> >> +Migrate the domain to the specified <cpupool> on the target host. 
> >> Specifying
> >> +an empty string for <cpupool> will use the default cpupool on <host>.
> >> +
> > 
> > Is this the wisest way to extend the interface?  We already have -C to
> > specify new configuration, and only have 26*2 short options to use.
> > 
> > What if the user could supply a xl.cfg snippet on the command line to be
> > merged over the existing configuration?  That would allow any parameter
> > to be changed, rather than just the cpupool.
> 
> I'm not opposed to that suggestion, but I believe the cpupool is rather
> special: it is more like a migration target specification than a domain
> parameter.
> 
> In case you are mostly concerned by burning another short option letter
> I can switch to using --cpupool= syntax.
> 
> And TBH: I consider the -C option being quite dangerous. While I can
> understand why it is present it is still a rather hacky approach for a
> general problem. Same applies to the capability to modify random
> settings of the domain config.

The -C option is rather dangerous. It disregards all guests states. You
will likely to lose your mac address unless you have set the same mac
address in the override file. Same goes for other states libxl might
have saved during domain creation.

Wei.

> 
> Juergen
> 

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