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From: Thomas Huth <thuth@redhat.com>
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Date: Mon, 21 Mar 2016 17:18:17 +0100
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Subject: Re: [Qemu-devel] [RFC PATCH 1/2] target-ppc: migrate interrupt
 vectors address for spapr VM
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To: =?UTF-8?Q?C=c3=a9dric_Le_Goater?= <clg@fr.ibm.com>, David Gibson <david@gibson.dropbear.id.au>
Cc: qemu-ppc@nongnu.org, Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>, qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>

On 21.03.2016 15:02, C=C3=A9dric Le Goater wrote:
> This address is changed by the linux kernel using the H_SET_MODE hcall
> and needs to be migrated in order to restart a spapr VM running in
> TCG. Other platforms should not be affected.
>=20
> Signed-off-by: C=C3=A9dric Le Goater <clg@fr.ibm.com>
> ---
>  target-ppc/machine.c | 3 +++
>  1 file changed, 3 insertions(+)
>=20
> diff --git a/target-ppc/machine.c b/target-ppc/machine.c
> index 692121e98319..a418d463db83 100644
> --- a/target-ppc/machine.c
> +++ b/target-ppc/machine.c
> @@ -553,6 +553,9 @@ const VMStateDescription vmstate_ppc_cpu =3D {
>          VMSTATE_UINTTL(env.hflags_nmsr, PowerPCCPU),
>          /* FIXME: access_type? */
> =20
> +        /* Effective Address of interrupt vectors */
> +        VMSTATE_UINTTL(env.excp_prefix, PowerPCCPU),
> +
>          /* Sanity checking */
>          VMSTATE_UINTTL_EQUAL(env.msr_mask, PowerPCCPU),
>          VMSTATE_UINT64_EQUAL(env.insns_flags, PowerPCCPU),

I'm really no expert with all this migration stuff, but don't you have
to bump the version_id when you add new fields to the vmstate?
... and/or use VMSTATE_UINTTL_V() so that migration from older versions
of QEMU to the current one also still works with KVM? For example, is it
still possible to migrate from QEMU 2.5 to QEMU 2.6 in KVM if you only
use VMSTATE_UINTTL without the _V suffix?

 Thomas