Re: [PATCH v2] hw/i386/amd_iommu: Allow migration

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Feb 06, 2025 at 05:18:56AM +0000, Suravee Suthikulpanit wrote:
> Add migration support for AMD IOMMU model by saving necessary AMDVIState
> parameters for MMIO registers, device table, command buffer, and event
> buffers.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> ---
> Changes from v1:
> (https://lore.kernel.org/all/9ecffa7a-f4c6-45a5-a066-84826ccb55dd@amd.com/T/)
> * Include ppr_log, pprlog_len, pprlog_head, pprlog_tail per Joao.
> 
>  hw/i386/amd_iommu.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c
> index 13af7211e1..a1940a0ab3 100644
> --- a/hw/i386/amd_iommu.c
> +++ b/hw/i386/amd_iommu.c
> @@ -1673,7 +1673,48 @@ static Property amdvi_properties[] = {
>  
>  static const VMStateDescription vmstate_amdvi_sysbus = {
>      .name = "amd-iommu",
> -    .unmigratable = 1
> +    .version_id = 1,

IMHO we should not remove the 'unmigratable = 1'  setting, until we
have fixed the design problem with this device, to split the creation
of the 'AMDVI-PCI' device off from the 'amd-iommu' device, so that the
former is user creatable.

As it stands now, there's no mechanism to guarantee that the internally
created 'AMDVI-PCI' device gets the same PCI address properties on every
boot. Thus it isn't safe to claim this device is migratable yet IMHO.

> +    .minimum_version_id = 1,
> +    .priority = MIG_PRI_IOMMU,
> +    .fields = (VMStateField[]) {


With regards,
Daniel
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