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

[Juergen Gross <jgross@xxxxxxxx>]

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.


Juergen


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