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

[Peter Xu <peterx@redhat.com>]

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"), 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