virtio_mmio: generation support

virtio_mmio currently lacks generation support which
makes multi-byte field access racy.
Fix by getting the value at offset 0xfc for version 2
devices. Nothing we can do for version 1, so return
generation id 0.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index cad569890908..9c877d2375a5 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -174,6 +174,16 @@ static void vm_set(struct virtio_device *vdev, unsigned offset,
                 writeb(ptr[i], vm_dev->base + VIRTIO_MMIO_CONFIG + offset + i);
 }
 
+static u32 vm_generation(struct virtio_device *vdev)
+{
+        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
+
+        if (vm_dev->version == 1)
+                return 0;
+        else
+                return readl(vm_dev->base + VIRTIO_MMIO_CONFIG_GENERATION);
+}
+
 static u8 vm_get_status(struct virtio_device *vdev)
 {
         struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
@@ -440,6 +450,7 @@ static const char *vm_bus_name(struct virtio_device *vdev)
 static const struct virtio_config_ops virtio_mmio_config_ops = {
         .get            = vm_get,
         .set            = vm_set,
+        .generation     = vm_generation,
         .get_status     = vm_get_status,
         .set_status     = vm_set_status,
         .reset          = vm_reset,