Only disable SMP for the capture kernel when not using KVM acceleration

Disabling SMP is necessary to work around a bug in QEMU's handling of
the capture kernel, but makes the tests run much slower. However, this
bug only appears to manifest when KVM acceleration is disabled, so the
testing harness has been modified to only disable SMP when this is true.

Signed-off-by: Kevin Svetlitski <[email protected]>

vmtest/enter_kdump.py

@@ -19,10 +19,12 @@
 with open("/proc/cmdline", "rb") as f:
     cmdline = f.read().rstrip(b"\n")
     cmdline = re.sub(rb"(^|\s)crashkernel=\S+", b"", cmdline)
-    # `nosmp` is required to avoid QEMU sporadically failing an internal assertion
     # `nokaslr` is required to avoid sporadically failing to reserve space for the
     # capture kernel
-    cmdline += b" nosmp nokaslr"
+    cmdline += b" nokaslr"
+    if not os.path.exists("/dev/kvm_enabled"):
+        # `nosmp` is required to avoid QEMU sporadically failing an internal assertion
+        cmdline += b" nosmp"
 
 with open(f"/lib/modules/{os.uname().release}/vmlinuz", "rb") as kernel:
     if syscall(

vmtest/vm.py

@@ -93,6 +93,10 @@
 "$BUSYBOX" ln -s /proc/self/fd/1 /dev/stdout
 "$BUSYBOX" ln -s /proc/self/fd/2 /dev/stderr
 
+if {kvm_enabled}; then
+    "$BUSYBOX" touch /dev/kvm_enabled
+fi
+
 # Configure networking.
 "$BUSYBOX" hostname "$HOSTNAME"
 "$BUSYBOX" ip link set lo up
@@ -217,6 +221,7 @@ def run_in_vm(command: str, kernel_dir: Path, build_dir: Path) -> int:
                     busybox=shlex.quote(busybox),
                     python=shlex.quote(sys.executable),
                     command=shlex.quote(command),
+                    kvm_enabled="true" if kvm_args else "false",
                 )
             )
         os.chmod(init, 0o755)