Re: [PATCH] qmp: Add ram-block-set/get-migratable commands

[Peter Xu <peterx@redhat.com>]

On Wed, Mar 11, 2026 at 09:47:29AM -0300, Fabiano Rosas wrote:
> luzhipeng <luzhipeng@cestc.cn> writes:
> 
> > Introduce two new QMP commands to manage RAMBlock migratable state:
> > 1. ram-block-set-migratable: Dynamically set a RAMBlock's migratable state
> > 2. ram-block-get-migratable: Query a RAMBlock's migratable state
> >
> 
> Hi! Could you provide more information on what are the use-cases for the
> new commands?
> 
> In particular, what is the condition that can cause a ramblock to become
> migratable/unmigratable at runtime that cannot be detected by QEMU
> itself?

Or instead of saying "detected" maybe it's "decided" by QEMU.

The QEMU cmdline and rest (e.g. a set of QMP commands to create the devices
that needs to happen on both sides, or migration caps/params like
x-ignore-shared) normally decides whether a ramblock should be migrated,
and AFAIU that's part of the guest ABI.

I think it may make more sense if we want to avoid migrating some ramblocks
then we provide some similar way (e.g. a object property of the memory
backend) rather than allowing it to be flipped anytime, causing more
unpredictable guest ABI.

Thanks,

-- 
Peter Xu