[PATCH 2/3] libxl: attach PCI device to qemu only after setting pciback/pcifront

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

When qemu is running in stubdomain, handling "pci-ins" command will fail
if pcifront is not initialized already. Fix this by sending such command
only after confirming that pciback/front is running.

It is possible to handle this case in mini-os code, by delaying
"pci-ins" handling until pcifront_thread finishes devices discovery. But
the same problem most likely will apply to any other stubdomain
implementations when they come (Rumprun, Linux) - so better handle this
at libxl level.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
 tools/libxl/libxl_pci.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
index 2ae1bc4..3805d30 100644
--- a/tools/libxl/libxl_pci.c
+++ b/tools/libxl/libxl_pci.c
@@ -1195,6 +1195,7 @@ int libxl__device_pci_add(libxl__gc *gc, uint32_t domid, libxl_device_pci *pcide
 {
     libxl_ctx *ctx = libxl__gc_owner(gc);
     unsigned int orig_vdev, pfunc_mask;
+    char *be_path;
     libxl_device_pci *assigned;
     int num_assigned, i, rc;
     int stubdomid = 0;
@@ -1249,6 +1250,14 @@ int libxl__device_pci_add(libxl__gc *gc, uint32_t domid, libxl_device_pci *pcide
         rc = do_pci_add(gc, stubdomid, &pcidev_s, 0);
         if ( rc )
             goto out;
+        /* wait for the device actually being connected, otherwise device model
+         * running there will fail to find the device */
+        be_path = libxl__sprintf(gc, "%s/backend/pci/%d/0",
+                libxl__xs_get_dompath(gc, 0), stubdomid);
+        rc = libxl__wait_for_backend(gc, be_path,
+                    GCSPRINTF("%d", XenbusStateConnected));
+        if ( rc )
+            goto out;
     }
 
     orig_vdev = pcidev->vdevfn & ~7U;
-- 
2.5.5


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