[Qemu-devel] [PATCH 3/4] blockdev: Defer creation of implicit PCI devices for IF_VIRTIO drives

[Peter Maydell <peter.maydell@linaro.org>]

If a user requests an IF_VIRTIO drive on the command line, don't
create the implicit PCI virtio device immediately, but wait until
the rest of the command line has been processed and only create the
device if the drive would otherwise be orphaned. This means that
if the user said drive,id=something,... -device drive=something,..,.
we'll allow the drive to be connected to the user's specified
device rather than stealing it to connect to the implicit virtio
device.

This deferral is *not* done for S390 devices, purely to ensure that
we retain backwards compatibility with command lines. We can
change the behaviour for PCI because right now no machine
specifies a block_default_type of IF_VIRTIO except for the
S390 machines.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 blockdev.c | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index 177b285..c480f64 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -46,6 +46,7 @@
 #include "qmp-commands.h"
 #include "trace.h"
 #include "sysemu/arch_init.h"
+#include "monitor/qdev.h"
 
 static const char *const if_name[IF_COUNT] = {
     [IF_NONE] = "none",
@@ -236,6 +237,17 @@ static void create_implicit_virtio_device(const char *driveid,
     if (devaddr) {
         qemu_opt_set(devopts, "addr", devaddr, &error_abort);
     }
+
+    if (done_orphan_check) {
+        /* If we're called after vl.c has processed the -device options
+         * then we need to create the device ourselves now.
+         */
+        DeviceState *dev = qdev_device_add(devopts);
+        if (!dev) {
+            exit(1);
+        }
+        object_unref(OBJECT(dev));
+    }
 }
 
 bool drive_check_orphaned(void)
@@ -252,6 +264,14 @@ bool drive_check_orphaned(void)
         /* Unless this is a default drive, this may be an oversight. */
         if (!blk_get_attached_dev(blk) && !dinfo->is_default &&
             dinfo->type != IF_NONE) {
+            if (dinfo->type == IF_VIRTIO) {
+                /* An orphaned virtio drive might be waiting for us to
+                 * create the implicit device for it.
+                 */
+                create_implicit_virtio_device(blk_name(blk), dinfo->devaddr);
+                continue;
+            }
+
             fprintf(stderr, "Warning: Orphaned drive without device: "
                     "id=%s,file=%s,if=%s,bus=%d,unit=%d\n",
                     blk_name(blk), blk_bs(blk)->filename, if_name[dinfo->type],
@@ -956,8 +976,13 @@ DriveInfo *drive_new(QemuOpts *all_opts, BlockInterfaceType block_default_type)
         goto fail;
     }
 
-    if (type == IF_VIRTIO && !done_orphan_check) {
-        /* Drives created via the monitor (hotplugged) do not get the
+    if (type == IF_VIRTIO && !done_orphan_check
+        && arch_type == QEMU_ARCH_S390X) {
+        /* Virtio drives created on the command line get an implicit device
+         * created for them. For non-s390x command line drives, the creation
+         * of the implicit device is deferred to drive_check_orphaned. (S390x
+         * is special-cased purely for backwards compatibility.)
+         * Drives created via the monitor (hotplugged) do not get the
          * magic implicit device created for them.
          */
         create_implicit_virtio_device(qdict_get_str(bs_opts, "id"), devaddr);
-- 
1.9.1