appliance: Document pipe fds.

[libguestfs.git] / src / launch.c

diff --git a/src/launch.c b/src/launch.c
index ecc0464..a2a9bea 100644 (file)
--- a/src/launch.c
+++ b/src/launch.c
@@ -487,21 +487,30 @@ launch_appliance (guestfs_h *g)
     if (qemu_supports (g, "-nodefconfig"))
       add_cmdline (g, "-nodefconfig");
 
-    /* qemu sometimes needs this option to enable hardware
-     * virtualization, but some versions of 'qemu-kvm' will use KVM
-     * regardless (even where this option appears in the help text).
-     * It is rumoured that there are versions of qemu where supplying
-     * this option when hardware virtualization is not available will
-     * cause qemu to fail, so we we have to check at least that
-     * /dev/kvm is openable.  That's not reliable, since /dev/kvm
-     * might be openable by qemu but not by us (think: SELinux) in
-     * which case the user would not get hardware virtualization,
-     * although at least shouldn't fail.  A giant clusterfuck with the
-     * qemu command line, again.
+    /* The qemu -machine option (added 2010-12) is a bit more sane
+     * since it falls back through various different acceleration
+     * modes, so try that first (thanks Markus Armbruster).
      */
-    if (qemu_supports (g, "-enable-kvm") &&
-        is_openable (g, "/dev/kvm", O_RDWR))
-      add_cmdline (g, "-enable-kvm");
+    if (qemu_supports (g, "-machine")) {
+      add_cmdline (g, "-machine");
+      add_cmdline (g, "accel=kvm:tcg");
+    } else {
+      /* qemu sometimes needs this option to enable hardware
+       * virtualization, but some versions of 'qemu-kvm' will use KVM
+       * regardless (even where this option appears in the help text).
+       * It is rumoured that there are versions of qemu where supplying
+       * this option when hardware virtualization is not available will
+       * cause qemu to fail, so we we have to check at least that
+       * /dev/kvm is openable.  That's not reliable, since /dev/kvm
+       * might be openable by qemu but not by us (think: SELinux) in
+       * which case the user would not get hardware virtualization,
+       * although at least shouldn't fail.  A giant clusterfuck with the
+       * qemu command line, again.
+       */
+      if (qemu_supports (g, "-enable-kvm") &&
+          is_openable (g, "/dev/kvm", O_RDWR))
+        add_cmdline (g, "-enable-kvm");
+    }
 
     /* Newer versions of qemu (from around 2009/12) changed the
      * behaviour of monitors so that an implicit '-monitor stdio' is
@@ -622,11 +631,13 @@ launch_appliance (guestfs_h *g)
       close (wfd[1]);
       close (rfd[0]);
 
+      /* Stdin. */
       if (dup (wfd[0]) == -1) {
       dup_failed:
         perror ("dup failed");
         _exit (EXIT_FAILURE);
       }
+      /* Stdout. */
       if (dup (rfd[1]) == -1)
         goto dup_failed;
 
@@ -634,12 +645,9 @@ launch_appliance (guestfs_h *g)
       close (rfd[1]);
     }
 
-#if 0
-    /* Set up a new process group, so we can signal this process
-     * and all subprocesses (eg. if qemu is really a shell script).
-     */
-    setpgid (0, 0);
-#endif
+    /* Put qemu in a new process group. */
+    if (g->pgroup)
+      setpgid (0, 0);
 
     setenv ("LC_ALL", "C", 1);
 
@@ -668,6 +676,14 @@ launch_appliance (guestfs_h *g)
       pid_t qemu_pid = g->pid;
       pid_t parent_pid = getppid ();
 
+      /* It would be nice to be able to put this in the same process
+       * group as qemu (ie. setpgid (0, qemu_pid)).  However this is
+       * not possible because we don't have any guarantee here that
+       * the qemu process has started yet.
+       */
+      if (g->pgroup)
+        setpgid (0, 0);
+
       /* Writing to argv is hideously complicated and error prone.  See:
        * http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/ps_status.c?rev=1.33.2.1;content-type=text%2Fplain
        */