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From: Juan Quintela <quintela@redhat.com>
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	(Jason Baron's message of "Thu, 13 Sep 2012 16:12:47 -0400")
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	<ef272249acf17363d5a9e3b38f9b5896349cfd4d.1347561356.git.jbaron@redhat.com>
Date: Fri, 14 Sep 2012 10:38:00 +0200
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Subject: Re: [Qemu-devel] [PATCH 19/25] ahci: add migration support
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To: Jason Baron <jbaron@redhat.com>
Cc: kwolf@redhat.com, aliguori@us.ibm.com, alex.williamson@redhat.com, mst@redhat.com, jan.kiszka@siemens.com, qemu-devel@nongnu.org, agraf@suse.de, yamahata@valinux.co.jp, juzhang@redhat.com, kevin@koconnor.net, avi@redhat.com, mkletzan@redhat.com, i.mitsyanko@samsung.com, lcapitulino@redhat.com, afaerber@suse.de, armbru@redhat.com

Jason Baron <jbaron@redhat.com> wrote:
> Add support for ahci migration. This patch builds upon the patches origin=
ally
> posted by Andreas F=C3=A4rber.
>
> These patches have been tested by migrating Windows 7 and Fedora 16 guest=
s on
> both piix with ahci attached and on q35 (which has a built-in ahci contro=
ller).

> +const VMStateDescription vmstate_ahci =3D {
> +    .name =3D "ahci",
> +    .version_id =3D 1,
> +    .post_load =3D ahci_state_post_load,
> +    .fields =3D (VMStateField []) {

  +        VMSTATE_INT32_EQUAL(ports, AHCIState),


> +        VMSTATE_STRUCT_VARRAY_POINTER_INT32(dev, AHCIState, ports,
> +                                     vmstate_ahci_device, AHCIDevice),
> +        VMSTATE_UINT32(control_regs.cap, AHCIState),
> +        VMSTATE_UINT32(control_regs.ghc, AHCIState),
> +        VMSTATE_UINT32(control_regs.irqstatus, AHCIState),
> +        VMSTATE_UINT32(control_regs.impl, AHCIState),
> +        VMSTATE_UINT32(control_regs.version, AHCIState),
> +        VMSTATE_UINT32(idp_index, AHCIState),
> +        VMSTATE_END_OF_LIST()
> +    },
> +};
> +

Only comment that I have is if we can add that bit on the vmstate
transition.  That way we can detect when the number of ports between the
two instances are different.

You can change it to; (it checks that ports received is less ore equal
than original value):

  +        VMSTATE_INT32_LE(ports, AHCIState),

If the code will work if we transfer less ports that are active. I have
no clue which one makes more sense from the ahci point of view.

Thanks, Juan.