Re: [Xen-devel] [PATCH v3 COLOPre 15/26] tools/libxl: Add back channel to allow migration target send data back

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2015-07-01 at 10:28 +0800, Yang Hongyang wrote:
> 
> On 06/30/2015 06:07 PM, Ian Campbell wrote:
> > On Thu, 2015-06-25 at 14:25 +0800, Yang Hongyang wrote:
> >> + * LIBXL_HAVE_DOMAIN_CREATE_RESTORE_SEND_FD 1
> >> + *
> >> + * If this is defined, libxl_domain_create_restore()'s API has changed to
> >> + * include a send_fd param which used for libxl migration back channel.
> >
> >                                     ^is
> >
> > Perhaps also end the sentence with "during $foo operations"? Since it is
> > not used for standard restore.
> 
> IIRC, at hackthon, someone from alibaba also mentioned that they need a back
> channel on normal migration

There is no code like that in tree, if such is added then comments may
need to be adjusted.

> ...For the standard restore, just pass -1 as
> send_fd.

Correct.

I'm asking for a clarification to thew comment here, not a code change.

> 
> >
> >>   int libxl_domain_create_restore(libxl_ctx *ctx, libxl_domain_config 
> >> *d_config,
> >> -                                uint32_t *domid, int restore_fd,
> >> +                                uint32_t *domid, int restore_fd, int 
> >> send_fd,
> >
> > This is probably not a good idea, but what about "int fd[2]", i.e.
> > mimicking pipe(2). I suspect this will just make things harder on
> 
> I suspect so...
> 
> > callers, especially those who wish to work with both versions. Thoughts?
> >
> > Ian.
> >
> > .
> >
> 



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