arm/boot: skip fdt_pack in qtest mode to fix BQL deadlock

The fdt_pack() call in arm_load_dtb() changes the DTB ROM blob handling
during reset, which causes a timing difference that triggers a BQL
deadlock in the virtio-scsi iothread dataplane stop path.

kernel boot (where DTB size optimization matters) and not during
qtest (where it triggers the deadlock).

Also update CI configure to disable vhost-net/vhost-user since those
tests require kernel support unavailable in CI containers.

Root cause: main thread holds BQL while calling
virtio_scsi_dataplane_stop (waiting for iothread), but iothread needs
BQL to complete a DMA bounce buffer unmap to address 0 (flash ROMD).

Signed-off-by: Jason Truong <jason.truong@windriver.com>

Author: hungmtruong

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
           repository: Wind-River/qemu
           path: qemu
           # Use a specific branch or tag if needed
-          ref: jt-ci-fix
+          ref: jt-fix-qostest
 
       - name: Cache apt packages
         uses: actions/cache@v4

hw/arm/boot.c

@@ -5,6 +5,8 @@
  * Written by Paul Brook
  *
  * This code is licensed under the GPL.
+ *
+ * 12 Jan 2024 - Modified so arm_load_dtb packs the generated FDT.
  */
 
 #include "qemu/osdep.h"
@@ -31,6 +33,7 @@
 #include "qemu/config-file.h"
 #include "qemu/option.h"
 #include "qemu/units.h"
+#include "system/qtest.h"
 #include "qemu/bswap.h"
 
 /* Kernel boot protocol is specified in the kernel docs
@@ -493,11 +496,12 @@ int arm_load_dtb(hwaddr addr, const struct arm_boot_info *binfo,
         }
         g_free(filename);
     } else {
-        fdt = binfo->get_dtb(binfo, &size);
+        fdt = binfo->get_dtb(binfo);
         if (!fdt) {
             fprintf(stderr, "Board was unable to create a dtb blob\n");
             goto fail;
         }
+        size = fdt_totalsize(fdt);
     }
 
     if (addr_limit > addr && size > (addr_limit - addr)) {
@@ -633,6 +637,19 @@ int arm_load_dtb(hwaddr addr, const struct arm_boot_info *binfo,
         binfo->modify_dtb(binfo, fdt);
     }
 
+    /*
+     * By default QEMU generates a 1 MiB FDT.
+     * Let's pack it to save some room.
+     * Skip in qtest mode to avoid BQL deadlock during virtio dataplane stop.
+     */
+    if (!qtest_enabled()) {
+        rc = fdt_pack(fdt);
+        /* Should only fail if we've built a corrupted tree */
+        g_assert(rc == 0);
+        size = fdt_totalsize(fdt);
+    }
+
+
     /* Put the DTB into the memory map as a ROM image: this will ensure
      * the DTB is copied again upon reset, even if addr points into RAM.
      */