From: Eric Auger <eric.auger@redhat.com>

Currently the iommu may be reset before the devices
it protects. For example this happens with virtio-net.

Let's use 3-phase reset mechanism and reset the IOMMU on
exit phase after all DMA capable devices have been
reset during the 'enter' or 'hold' phase.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>

Message-Id: <20250218182737.76722-2-eric.auger@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/virtio-iommu.c | 14 ++++++++++----
 hw/virtio/trace-events   |  2 +-
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
index f41104a952..b6e7e01ef7 100644
--- a/hw/virtio/virtio-iommu.c
+++ b/hw/virtio/virtio-iommu.c
@@ -1504,11 +1504,11 @@ static void virtio_iommu_device_unrealize(DeviceState *dev)
     virtio_cleanup(vdev);
 }
 
-static void virtio_iommu_device_reset(VirtIODevice *vdev)
+static void virtio_iommu_device_reset_exit(Object *obj, ResetType type)
 {
-    VirtIOIOMMU *s = VIRTIO_IOMMU(vdev);
+    VirtIOIOMMU *s = VIRTIO_IOMMU(obj);
 
-    trace_virtio_iommu_device_reset();
+    trace_virtio_iommu_device_reset_exit();
 
     if (s->domains) {
         g_tree_destroy(s->domains);
@@ -1668,6 +1668,7 @@ static void virtio_iommu_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
+    ResettableClass *rc = RESETTABLE_CLASS(klass);
 
     device_class_set_props(dc, virtio_iommu_properties);
     dc->vmsd = &vmstate_virtio_iommu;
@@ -1675,7 +1676,12 @@ static void virtio_iommu_class_init(ObjectClass *klass, void *data)
     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
     vdc->realize = virtio_iommu_device_realize;
     vdc->unrealize = virtio_iommu_device_unrealize;
-    vdc->reset = virtio_iommu_device_reset;
+
+    /*
+     * Use 'exit' reset phase to make sure all DMA requests
+     * have been quiesced during 'enter' or 'hold' phase
+     */
+    rc->phases.exit = virtio_iommu_device_reset_exit;
     vdc->get_config = virtio_iommu_get_config;
     vdc->set_config = virtio_iommu_set_config;
     vdc->get_features = virtio_iommu_get_features;
diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index 04e36ae047..76f0d458b2 100644
--- a/hw/virtio/trace-events
+++ b/hw/virtio/trace-events
@@ -108,7 +108,7 @@ virtio_pci_notify_write(uint64_t addr, uint64_t val, unsigned int size) "0x%" PR
 virtio_pci_notify_write_pio(uint64_t addr, uint64_t val, unsigned int size) "0x%" PRIx64" = 0x%" PRIx64 " (%d)"
 
 # hw/virtio/virtio-iommu.c
-virtio_iommu_device_reset(void) "reset!"
+virtio_iommu_device_reset_exit(void) "reset!"
 virtio_iommu_system_reset(void) "system reset!"
 virtio_iommu_get_features(uint64_t features) "device supports features=0x%"PRIx64
 virtio_iommu_device_status(uint8_t status) "driver status = %d"
-- 
MST