Re: [External] Re: [PATCH v2 4/7] migration/multifd: Enable zero page checking from multifd threads.

[Peter Xu <peterx@redhat.com>]

On Sat, Feb 24, 2024 at 03:03:15PM -0800, Hao Xiang wrote:
> So I just want to make sure I am coding the right solution. I added
> setting "zero-page-detection" to "legacy" in hw_compat_8_2 and tested
> it. The behavior is that if I set machine type to pc-q35-8.2,
> zero-page-detection will automatically be set to "legacy". But if I
> set the machine type to pc-q35-9.0, zero-page-detection will be the
> default value "multifd". However, this doesn't seem to be a hard
> requirement because I can still override zero-page-detection to
> multifd on machine type pc-q35-8.2. Is this OK?

What we want to guarantee is old 8.2 users can smoothly migrate to the new
qemus, and existing 8.2 (or prior) users definitely don't have any override
over the new parameter zero-page-detection simply because 8.2 (or prior)
binary doesn't support it yet.

Then, if someone is using new binary with 8.2 machine types, meanwhile
override this default value, it means it's the user's choice of doing this,
and the user should guarantee all the qemus he/she manages also keeps this
parameter override to make sure migration will work between these qemu
processes.

So in short, that's all fine.

Thanks,

-- 
Peter Xu