Re: [Qemu-devel] [PULL 21/38] spapr: Add forgotten capability to migration stream

[Greg Kurz]

On Wed, 22 May 2019 14:45:43 +1000
David Gibson <address@hidden> wrote:

> spapr machine capabilities are supposed to be sent in the migration stream
> so that we can sanity check the source and destination have compatible
> configuration.  Unfortunately, when we added the hpt-max-page-size
> capability, we forgot to add it to the migration state.  This means that we
> can generate spurious warnings when both ends are configured for large
> pages, or potentially fail to warn if the source is configured for huge
> pages, but the destination is not.
> 
> Fixes: 2309832afda "spapr: Maximum (HPT) pagesize property"
> 
> Signed-off-by: David Gibson <address@hidden>
> Reviewed-by: Cédric Le Goater <address@hidden>
> ---

Huh... we discussed that it was breaking backward migration:

https://lists.gnu.org/archive/html/qemu-ppc/2019-05/msg00330.html

So I'm a bit surprised to see this in the PR... is it intentional ?

>  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 8580a8dc67..bcae30ad26 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2125,6 +2125,7 @@ static const VMStateDescription vmstate_spapr = {
>          &vmstate_spapr_cap_cfpc,
>          &vmstate_spapr_cap_sbbc,
>          &vmstate_spapr_cap_ibs,
> +        &vmstate_spapr_cap_hpt_maxpagesize,
>          &vmstate_spapr_irq_map,
>          &vmstate_spapr_cap_nested_kvm_hv,
>          &vmstate_spapr_dtb,
> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> index 9b1c10baa6..658eb15a14 100644
> --- a/hw/ppc/spapr_caps.c
> +++ b/hw/ppc/spapr_caps.c
> @@ -703,6 +703,7 @@ SPAPR_CAP_MIG_STATE(dfp, SPAPR_CAP_DFP);
>  SPAPR_CAP_MIG_STATE(cfpc, SPAPR_CAP_CFPC);
>  SPAPR_CAP_MIG_STATE(sbbc, SPAPR_CAP_SBBC);
>  SPAPR_CAP_MIG_STATE(ibs, SPAPR_CAP_IBS);
> +SPAPR_CAP_MIG_STATE(hpt_maxpagesize, SPAPR_CAP_HPT_MAXPAGESIZE);
>  SPAPR_CAP_MIG_STATE(nested_kvm_hv, SPAPR_CAP_NESTED_KVM_HV);
>  SPAPR_CAP_MIG_STATE(large_decr, SPAPR_CAP_LARGE_DECREMENTER);
>  SPAPR_CAP_MIG_STATE(ccf_assist, SPAPR_CAP_CCF_ASSIST);
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 7e32f309c2..9fc91c8f5e 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -849,6 +849,7 @@ extern const VMStateDescription vmstate_spapr_cap_dfp;
>  extern const VMStateDescription vmstate_spapr_cap_cfpc;
>  extern const VMStateDescription vmstate_spapr_cap_sbbc;
>  extern const VMStateDescription vmstate_spapr_cap_ibs;
> +extern const VMStateDescription vmstate_spapr_cap_hpt_maxpagesize;
>  extern const VMStateDescription vmstate_spapr_cap_nested_kvm_hv;
>  extern const VMStateDescription vmstate_spapr_cap_large_decr;
>  extern const VMStateDescription vmstate_spapr_cap_ccf_assist;