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[PULL 23/41] vfio/iommufd: Query dirty bitmap before DMA unmap

Cédric Le Goater posted 41 patches 3 weeks, 6 days ago

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[PULL 23/41] vfio/iommufd: Query dirty bitmap before DMA unmap

Posted by Cédric Le Goater 3 weeks, 6 days ago

From: Zhenzhong Duan <zhenzhong.duan@intel.com>

When an existing mapping is unmapped, there could already be dirty bits
which need to be recorded before unmap.

If query dirty bitmap fails, we still need to do unmapping or else there
is stale mapping and it's risky to guest.

Co-developed-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Tested-by: Xudong Hao <xudong.hao@intel.com>
Tested-by: Giovannio Cabiddu <giovanni.cabiddu@intel.com>
Tested-by: Rohith S R <rohith.s.r@intel.com>
Link: https://lore.kernel.org/qemu-devel/20251218062643.624796-3-zhenzhong.duan@intel.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/vfio/iommufd.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
index f56349faf5669cfeed10d7fc5e8d3bf8397bb04d..6d6244d7b9723def647f3dd4eec7ef1558415bb2 100644
--- a/hw/vfio/iommufd.c
+++ b/hw/vfio/iommufd.c
@@ -65,7 +65,7 @@ static int iommufd_cdev_unmap(const VFIOContainer *bcontainer,
     uint32_t ioas_id = container->ioas_id;
     bool need_dirty_sync = false;
     Error *local_err = NULL;
-    int ret;
+    int ret, unmap_ret;
 
     if (unmap_all) {
         size = UINT64_MAX;
@@ -74,8 +74,21 @@ static int iommufd_cdev_unmap(const VFIOContainer *bcontainer,
     if (iotlb && vfio_container_dirty_tracking_is_started(bcontainer)) {
         if (!vfio_container_devices_dirty_tracking_is_supported(bcontainer) &&
             bcontainer->dirty_pages_supported) {
-            /* TODO: query dirty bitmap before DMA unmap */
-            return iommufd_backend_unmap_dma(be, ioas_id, iova, size);
+            ret = vfio_container_query_dirty_bitmap(bcontainer, iova, size,
+                                                    iotlb->translated_addr,
+                                                    &local_err);
+            if (ret) {
+                error_report_err(local_err);
+            }
+            /* Unmap stale mapping even if query dirty bitmap fails */
+            unmap_ret = iommufd_backend_unmap_dma(be, ioas_id, iova, size);
+
+            /*
+             * If dirty tracking fails, return the failure to VFIO core to
+             * fail the migration, or else there will be dirty pages missed
+             * to be migrated.
+             */
+            return unmap_ret ? : ret;
         }
 
         need_dirty_sync = true;
-- 
2.52.0