Re: [Qemu-devel] [PATCH] intel_iommu: fix migration breakage on mr switch

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jun 29, 2017 at 12:26:57PM +0800, Peter Xu wrote:
> Migration is broken after the vfio integration work:
> 
> qemu-kvm: AHCI: Failed to start FIS receive engine: bad FIS receive buffer address
> qemu-kvm: Failed to load ich9_ahci:ahci
> qemu-kvm: error while loading state for instance 0x0 of device '0000:00:1f.2/ich9_ahci'
> qemu-kvm: load of migration failed: Operation not permitted
> 
> The problem is that vfio work introduced dynamic memory region
> switching (actually it is also used for future PT mode), and this memory
> region layout is not properly delivered to destination when migration
> happens. Solution is to rebuild the layout in post_load.
> 
> Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1459906
> Fixes: 558e0024 ("intel_iommu: allow dynamic switch of IOMMU region")
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  hw/i386/intel_iommu.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index a9b59bd..36b231d 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -2332,11 +2332,28 @@ static void vtd_iommu_notify_flag_changed(MemoryRegion *iommu,
>      }
>  }
>  
> +static int vtd_post_load(void *opaque, int version_id)
> +{
> +    IntelIOMMUState *iommu = opaque;
> +
> +    /*
> +     * Since commit 558e00 ("intel_iommu: allow dynamic switch of
> +     * IOMMU region"),

I would drop this part of the comment. It isn't of interest
to people reading code directly, while people reading git
history see the commit log.

> memory regions are dynamically turned on/off
> +     * depending on context entry configurations from the guest. After
> +     * migration, we need to make sure the memory regions are still
> +     * correct.
> +     */
> +    vtd_switch_address_space_all(iommu);
> +
> +    return 0;
> +}
> +
>  static const VMStateDescription vtd_vmstate = {
>      .name = "iommu-intel",
>      .version_id = 1,
>      .minimum_version_id = 1,
>      .priority = MIG_PRI_IOMMU,
> +    .post_load = vtd_post_load,
>      .fields = (VMStateField[]) {
>          VMSTATE_UINT64(root, IntelIOMMUState),
>          VMSTATE_UINT64(intr_root, IntelIOMMUState),
> -- 
> 2.7.4