Re: [PATCH V3 09/42] vfio/container: discard old DMA vaddr

[Cédric Le Goater]

On 5/12/25 17:32, Steve Sistare wrote:

In the container pre_save handler, discard the virtual addresses in DMA
mappings with VFIO_DMA_UNMAP_FLAG_VADDR, because guest RAM will be
remapped at a different VA after in new QEMU.  DMA to already-mapped
pages continues.

Signed-off-by: Steve Sistare <steven.sist...@oracle.com>

Looks OK. Too bad the pre_save() handler doesn't have an
'Error **' parameter.

It shouldn't be too complex to add in vmstate_save_state_v().


Reviewed-by: Cédric Le Goater <c...@redhat.com>

Thanks,

C.

---
  hw/vfio/cpr-legacy.c | 29 +++++++++++++++++++++++++++++
  1 file changed, 29 insertions(+)

diff --git a/hw/vfio/cpr-legacy.c b/hw/vfio/cpr-legacy.c
index 638a8e0..519d772 100644
--- a/hw/vfio/cpr-legacy.c
+++ b/hw/vfio/cpr-legacy.c
@@ -17,6 +17,22 @@
  #include "migration/vmstate.h"
  #include "qapi/error.h"

+static bool vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)

+{
+    struct vfio_iommu_type1_dma_unmap unmap = {
+        .argsz = sizeof(unmap),
+        .flags = VFIO_DMA_UNMAP_FLAG_VADDR | VFIO_DMA_UNMAP_FLAG_ALL,
+        .iova = 0,
+        .size = 0,
+    };
+    if (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
+        error_setg_errno(errp, errno, "vfio_dma_unmap_vaddr_all");
+        return false;
+    }
+    return true;
+}
+
+
  static bool vfio_cpr_supported(VFIOContainer *container, Error **errp)
  {
      if (!ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UPDATE_VADDR)) {
@@ -32,6 +48,18 @@ static bool vfio_cpr_supported(VFIOContainer *container, 
Error **errp)
      }
  }

+static int vfio_container_pre_save(void *opaque)

+{
+    VFIOContainer *container = opaque;
+    Error *err = NULL;
+
+    if (!vfio_dma_unmap_vaddr_all(container, &err)) {
+        error_report_err(err);
+        return -1;
+    }
+    return 0;
+}
+
  static int vfio_container_post_load(void *opaque, int version_id)
  {
      VFIOContainer *container = opaque;
@@ -52,6 +80,7 @@ static const VMStateDescription vfio_container_vmstate = {
      .name = "vfio-container",
      .version_id = 0,
      .minimum_version_id = 0,
+    .pre_save = vfio_container_pre_save,
      .post_load = vfio_container_post_load,
      .needed = cpr_needed_for_reuse,
      .fields = (VMStateField[]) {