Re: [Xen-devel] [PATCH-for-4.13] x86/mm: don't needlessly veto migration

[Jan Beulich <jbeulich@xxxxxxxx>]

On 01.10.2019 15:29, Paul Durrant wrote:
> The changes in XAPI are not vast; the main complexity is in the device
> emulator (to provide information during the live phase of migration)
> but I still don't see why Citrix's choice of closed vs. open source
> implementation of the emulator really has anything to do with this. It
> is still my opinion that Xen's only valid reason for refusing to
> enable logdirty for a domain is one of host safety and I still haven't
> heard an argument as to why Xen *is* right to refuse in other
> circumstances.

Let me take a completely different example for comparison:
There's no risk to the host in assigning the same, say, USB
controller to two guests. Yet Xen refuses to do so, even if the
tool stack didn't already filter such attempts, and even if the
admin may know that the two domains are cooperating, and hence
wouldn't get in the way of one another. (There are, I think,
many other similar examples.)

That said I can certainly see the validity of your and Andrew's
argumentation. It's just that, as in various other cases, I
don't think that's the only reasonable way of arranging things.
Hence at the very least your change would imo need to come with
an extended description.

Jan

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