[PATCH for 7.2? V2] vhost: fix vq dirty bitmap syncing when vIOMMU is enabled

[Jason Wang]

When vIOMMU is enabled, the vq->used_phys is actually the IOVA not
GPA. So we need to translate it to GPA before the syncing otherwise we
may hit the following crash since IOVA could be out of the scope of
the GPA log size. This could be noted when using virtio-IOMMU with
vhost using 1G memory.

Fixes: c471ad0e9bd46 ("vhost_net: device IOTLB support")
Cc: qemu-stable@nongnu.org
Tested-by: Lei Yang <leiyang@redhat.com>
Reported-by: Yalan Zhang <yalzhang@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
Changes since V1:
- Fix the address calculation when used ring is not page aligned
- Fix the length for each round of dirty bitmap syncing
- Use LOG_GUEST_ERROR to log wrong used adddress
- Various other tweaks
---
 hw/virtio/vhost.c | 76 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 56 insertions(+), 20 deletions(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index d1c4c20b8c..0cd5f25fcb 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -20,6 +20,7 @@
 #include "qemu/range.h"
 #include "qemu/error-report.h"
 #include "qemu/memfd.h"
+#include "qemu/log.h"
 #include "standard-headers/linux/vhost_types.h"
 #include "hw/virtio/virtio-bus.h"
 #include "hw/virtio/virtio-access.h"
@@ -106,6 +107,24 @@ static void vhost_dev_sync_region(struct vhost_dev *dev,
     }
 }
 
+static bool vhost_dev_has_iommu(struct vhost_dev *dev)
+{
+    VirtIODevice *vdev = dev->vdev;
+
+    /*
+     * For vhost, VIRTIO_F_IOMMU_PLATFORM means the backend support
+     * incremental memory mapping API via IOTLB API. For platform that
+     * does not have IOMMU, there's no need to enable this feature
+     * which may cause unnecessary IOTLB miss/update transactions.
+     */
+    if (vdev) {
+        return virtio_bus_device_iommu_enabled(vdev) &&
+            virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
+    } else {
+        return false;
+    }
+}
+
 static int vhost_sync_dirty_bitmap(struct vhost_dev *dev,
                                    MemoryRegionSection *section,
                                    hwaddr first,
@@ -137,8 +156,43 @@ static int vhost_sync_dirty_bitmap(struct vhost_dev *dev,
             continue;
         }
 
-        vhost_dev_sync_region(dev, section, start_addr, end_addr, 
vq->used_phys,
-                              range_get_last(vq->used_phys, vq->used_size));
+        if (vhost_dev_has_iommu(dev)) {
+            IOMMUTLBEntry iotlb;
+            hwaddr used_phys = vq->used_phys, used_size = vq->used_size;
+            hwaddr phys, s;
+
+            while (used_size) {
+                rcu_read_lock();
+                iotlb = address_space_get_iotlb_entry(dev->vdev->dma_as,
+                                                      used_phys,
+                                                      true, 
MEMTXATTRS_UNSPECIFIED);
+                rcu_read_unlock();
+
+                if (!iotlb.target_as) {
+                    qemu_log_mask(LOG_GUEST_ERROR, "translation "
+                                  "failure for used_phys %"PRIx64"\n", 
used_phys);
+                    return -EINVAL;
+                }
+
+                phys = iotlb.translated_addr + (used_phys & iotlb.addr_mask);
+
+                /* Distance from start of used ring until last byte of
+                   IOMMU page */
+                s = iotlb.addr_mask - (used_phys & iotlb.addr_mask);
+                /* Size of used ring, or of the part of it until end
+                   of IOMMU page */
+                s = MIN(s, used_size - 1) + 1;
+
+                vhost_dev_sync_region(dev, section, start_addr, end_addr, phys,
+                                      range_get_last(phys, s));
+                used_size -= s;
+                used_phys += s;
+            }
+        } else {
+            vhost_dev_sync_region(dev, section, start_addr,
+                                  end_addr, vq->used_phys,
+                                  range_get_last(vq->used_phys, 
vq->used_size));
+        }
     }
     return 0;
 }
@@ -306,24 +360,6 @@ static inline void vhost_dev_log_resize(struct vhost_dev 
*dev, uint64_t size)
     dev->log_size = size;
 }
 
-static bool vhost_dev_has_iommu(struct vhost_dev *dev)
-{
-    VirtIODevice *vdev = dev->vdev;
-
-    /*
-     * For vhost, VIRTIO_F_IOMMU_PLATFORM means the backend support
-     * incremental memory mapping API via IOTLB API. For platform that
-     * does not have IOMMU, there's no need to enable this feature
-     * which may cause unnecessary IOTLB miss/update transactions.
-     */
-    if (vdev) {
-        return virtio_bus_device_iommu_enabled(vdev) &&
-            virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
-    } else {
-        return false;
-    }
-}
-
 static void *vhost_memory_map(struct vhost_dev *dev, hwaddr addr,
                               hwaddr *plen, bool is_write)
 {
-- 
2.25.1