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Re: [Xen-devel] [PATCH v3 COLOPre 19/26] libxc/migration: Specification update for DIRTY_BITMAP records





On 06/30/2015 06:24 PM, Ian Campbell wrote:
On Thu, 2015-06-25 at 14:25 +0800, Yang Hongyang wrote:
Used by secondary to send it's dirty bitmap to primary under COLO.

This is the backchannel, right?

Right.


It seems to me that this ought to be described more clearly as a
separate stream in the opposite direction, rather than looking like just
another record in the forward channel.

Agreed, I'm not sure if having this back channel record is eligible,
Andy, thoughts?


Does the back channel not also need some sort of negotiation phase where
we check both ends are compatible (i.e. like the forward channel's
header). This might be easier than with the forward channel since you
might assert that the versions must match exactly for COLO to be
possible, that might not be true of some potential future user of the
backchannel though.

The negotiation record for COLO is introduced in the following patch
on libxl side. But that might be diffrent form what you said here, we
don't have a version check currently, if the 2 side doesn't match, for
example one has colo feature enabled and the other end do not, the
migration will simply fail.



.


--
Thanks,
Yang.

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