iommufd: preserve DMA mappings

During cpr-transfer load in new QEMU, the vfio_memory_listener causes
spurious calls to map and unmap DMA regions, as devices are created and
the address space is built.  This memory was already already mapped by the
device in old QEMU, so suppress the map and unmap callbacks during incoming
CPR.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Link: https://lore.kernel.org/qemu-devel/1751493538-202042-20-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

diff --git a/backends/iommufd.c b/backends/iommufd.c
index e0917923bffbb60dc5c58235880335c4d5eb7df7..2a33c7ab0bcdc9aabda55258741022debab0bdad 100644 (file)
--- a/backends/iommufd.c
+++ b/backends/iommufd.c
@@ -245,6 +245,10 @@ int iommufd_backend_map_file_dma(IOMMUFDBackend *be, uint32_t ioas_id,
         .length = size,
     };
 
+    if (cpr_is_incoming()) {
+        return 0;
+    }
+
     if (!readonly) {
         map.flags |= IOMMU_IOAS_MAP_WRITEABLE;
     }
@@ -274,6 +278,10 @@ int iommufd_backend_unmap_dma(IOMMUFDBackend *be, uint32_t ioas_id,
         .length = size,
     };
 
+    if (cpr_is_incoming()) {
+        return 0;
+    }
+
     ret = ioctl(fd, IOMMU_IOAS_UNMAP, &unmap);
     /*
      * IOMMUFD takes mapping as some kind of object, unmapping