Re: [PULL 02/96] spapr: Migrate ail-mode-3 spapr cap

[Michael Tokarev]

26.07.2024 02:52, Nicholas Piggin пишет:
> This cap did not add the migration code when it was introduced. This
> results in migration failure when changing the default using the
> command line.
>
> Cc: qemu-stable@nongnu.org
> Fixes: ccc5a4c5e10 ("spapr: Add SPAPR_CAP_AIL_MODE_3 for AIL mode 3 support for 
> H_SET_MODE hcall")
> Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>   hw/ppc/spapr.c         | 1 +
>   hw/ppc/spapr_caps.c    | 1 +
>   include/hw/ppc/spapr.h | 1 +
>   3 files changed, 3 insertions(+)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 98fa3aa6a8..370d7c35d3 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2195,6 +2195,7 @@ static const VMStateDescription vmstate_spapr = {
>           &vmstate_spapr_cap_fwnmi,
>           &vmstate_spapr_fwnmi,
>           &vmstate_spapr_cap_rpt_invalidate,
> +        &vmstate_spapr_cap_ail_mode_3,
>           &vmstate_spapr_cap_nested_papr,
>           NULL
>       }

Hi!

I've another question about this patch.

It's marked for-stable, and it applies cleanly for 9.0
(but eg in 8.2, cap_nested_papr subsection isn't here
yet).

Will a 9.0 qemu with this patch be incompatible with 9.0
qemu without this patch wrt migration?

How about 8.2 (if I fix up the context, so cap_ail_mode_3
is at the same index but at the end)?

How about migrating between 8.2 without this patch and 9.0
with this patch?

Does this change break migration, ever?  (Yes, I'm not sure
I understand even this level of migration code).

Thanks,

/mjt

--
GPG Key transition (from rsa2048 to rsa4096) since 2024-04-24.
New key: rsa4096/61AD3D98ECDF2C8E  9D8B E14E 3F2A 9DD7 9199  28F1 61AD 3D98 
ECDF 2C8E
Old key: rsa2048/457CE0A0804465C5  6EE1 95D1 886E 8FFB 810D  4324 457C E0A0 
8044 65C5
Transition statement: http://www.corpit.ru/mjt/gpg-transition-2024.txt