[RFC,V4,1/2] xen: pass kernel initrd to qemu

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index c087cbc..5833908 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -304,6 +304,37 @@  Action to take if the domain crashes.  Default is C<destroy>.
 
 =back
 
+=head3 Direct Kernel Boot
+
+Direct kernel boot allows booting directly from a kernel and initrd
+stored in the host physical machine OS, allowing command line arguments
+to be passed directly. PV guest direct kernel boot is supported. HVM
+guest direct kernel boot is supported with limitation (it's supported
+when using qemu-xen and default BIOS 'seabios'; not supported in case of
+stubdom-dm and old rombios.)
+
+=over 4
+
+=item B<kernel="PATHNAME">
+
+Load the specified file as the kernel image.
+
+=item B<ramdisk="PATHNAME">
+
+Load the specified file as the ramdisk.
+
+=item B<root="STRING">
+
+Append B<root="STRING"> to the kernel command line (Note: it is guest
+specific what meaning this has).
+
+=item B<extra="STRING">
+
+Append B<STRING> to the kernel command line. (Note: it is guest
+specific what meaning this has).
+
+=back
+
 =head3 Other Options
 
 =over 4
@@ -646,20 +677,12 @@  The following options apply only to Paravirtual guests.
 
 =over 4
 
-=item B<kernel="PATHNAME">
-
-Load the specified file as the kernel image.  Either B<kernel> or
-B<bootloader> must be specified for PV guests.
-
-=item B<ramdisk="PATHNAME">
-
-Load the specified file as the ramdisk.
-
 =item B<bootloader="PROGRAM">
 
 Run C<PROGRAM> to find the kernel image and ramdisk to use.  Normally
 C<PROGRAM> would be C<pygrub>, which is an emulation of
-grub/grub2/syslinux.
+grub/grub2/syslinux. Either B<kernel> or B<bootloader> must be specified
+for PV guests.
 
 =item B<bootloader_args=[ "ARG", "ARG", ...]>
 
@@ -667,16 +690,6 @@  Append B<ARG>s to the arguments to the B<bootloader>
 program. Alternatively if the argument is a simple string then it will
 be split into words at whitespace (this second option is deprecated).
 
-=item B<root="STRING">
-
-Append B<root="STRING"> to the kernel command line (Note: it is guest
-specific what meaning this has).
-
-=item B<extra="STRING">
-
-Append B<STRING> to the kernel command line. Note: it is guest
-specific what meaning this has).
-
 =item B<e820_host=BOOLEAN>
 
 Selects whether to expose the host e820 (memory map) to the guest via
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 69ceac8..a45415d 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -493,6 +493,44 @@  typedef struct libxl__ctx libxl_ctx;
  */
 #define LIBXL_HAVE_DEVICE_PCI_SEIZE 1
 
+/*
+ * LIBXL_HAVE_BUILDINFO_KERNEL
+ *
+ * If this is defined, then the libxl_domain_build_info structure will
+ * contain 'kernel' string field. It is to indicate kernel image location,
+ * for both PV and HVM guest to do direct kernel boot. For compatibility,
+ * u.pv.kernel still exists, but it might be deprecated in future.
+ *
+ * If it is set, guest will be booted from the indicated kernel.
+ */
+#define LIBXL_HAVE_BUILDINFO_KERNEL 1
+
+/*
+ * LIBXL_HAVE_BUILDINFO_RAMDISK
+ *
+ * If this is defined, then the libxl_domain_build_info structure will
+ * contain 'ramdisk' string field. It is to indicate ramdisk location,
+ * for both PV and HVM guest to do direct kernel boot. For compatibility,
+ * u.pv.ramdisk still exists, but it might be deprecated in future.
+ *
+ * If it is set, guest will be booted from indicated kernel and ramdisk.
+ */
+#define LIBXL_HAVE_BUILDINFO_RAMDISK 1
+
+/*
+ * LIBXL_HAVE_BUILDINFO_CMDLINE
+ *
+ * If this is defined, then the libxl_domain_build_info structure will
+ * contain 'cmdline' string field. It is a string to indicate paramters
+ * which would be appened to kernel image, for both PV and HVM guest to
+ * do direct kernel boot. For compatibility, u.pv.cmdline still exists,
+ * but it might be deprecated in future.
+ *
+ * If it is set, guest will be booted from indicated kernel with
+ * parameters as indicated in 'cmdline'.
+ */
+#define LIBXL_HAVE_BUILDINFO_CMDLINE 1
+
 /* Functions annotated with LIBXL_EXTERNAL_CALLERS_ONLY may not be
  * called from within libxl itself. Callers outside libxl, who
  * do not #include libxl_internal.h, are fine. */
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index addacdb..4f1cbd2 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -196,6 +196,12 @@  static char ** libxl__build_device_model_args_old(libxl__gc *gc,
         int nr_set_cpus = 0;
         char *s;
 
+        if (b_info->kernel) {
+            LOG(ERROR, "HVM direct kernel boot is not supported by "
+                "qemu-xen-traditional");
+            return NULL;
+        }
+
         if (b_info->u.hvm.serial) {
             flexarray_vappend(dm_args, "-serial", b_info->u.hvm.serial, NULL);
         }
@@ -479,6 +485,15 @@  static char ** libxl__build_device_model_args_new(libxl__gc *gc,
     if (b_info->type == LIBXL_DOMAIN_TYPE_HVM) {
         int ioemu_nics = 0;
 
+        if (b_info->kernel)
+            flexarray_vappend(dm_args, "-kernel", b_info->kernel, NULL);
+
+        if (b_info->ramdisk)
+            flexarray_vappend(dm_args, "-initrd", b_info->ramdisk, NULL);
+
+        if (b_info->cmdline)
+            flexarray_vappend(dm_args, "-append", b_info->cmdline, NULL);
+
         if (b_info->u.hvm.serial) {
             flexarray_vappend(dm_args, "-serial", b_info->u.hvm.serial, NULL);
         }
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 1018142..66ba18b 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -338,6 +338,9 @@  libxl_domain_build_info = Struct("domain_build_info",[
     ("iomem",            Array(libxl_iomem_range, "num_iomem")),
     ("claim_mode",	     libxl_defbool),
     ("event_channels",   uint32),
+    ("kernel",           string),
+    ("cmdline",          string),
+    ("ramdisk",          string),
     ("u", KeyedUnion(None, libxl_domain_type, "type",
                 [("hvm", Struct(None, [("firmware",         string),
                                        ("bios",             libxl_bios_type),
diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index be041f2..123d84d 100644
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -693,6 +693,29 @@  static void parse_top_level_sdl_options(XLU_Config *config,
     xlu_cfg_replace_string (config, "xauthority", &sdl->xauthority, 0);
 }
 
+static char *parse_cmdline(XLU_Config *config)
+{
+    char *cmdline = NULL;
+    const char *root = NULL, *extra = "";
+
+    xlu_cfg_get_string (config, "root", &root, 0);
+    xlu_cfg_get_string (config, "extra", &extra, 0);
+
+    if (root) {
+        if (asprintf(&cmdline, "root=%s %s", root, extra) == -1)
+            cmdline = NULL;
+    } else {
+        cmdline = strdup(extra);
+    }
+
+    if ((root || extra) && !cmdline) {
+        fprintf(stderr, "Failed to allocate memory for cmdline\n");
+        exit(1);
+    }
+
+    return cmdline;
+}
+
 static void parse_config_data(const char *config_source,
                               const char *config_data,
                               int config_len,
@@ -942,13 +965,21 @@  static void parse_config_data(const char *config_source,
     if (!xlu_cfg_get_long(config, "max_event_channels", &l, 0))
         b_info->event_channels = l;
 
+    xlu_cfg_replace_string (config, "kernel", &b_info->kernel, 0);
+    xlu_cfg_replace_string (config, "ramdisk", &b_info->ramdisk, 0);
+    b_info->cmdline = parse_cmdline(config);
+
     xlu_cfg_get_defbool(config, "driver_domain", &c_info->driver_domain, 0);
 
     switch(b_info->type) {
     case LIBXL_DOMAIN_TYPE_HVM:
-        if (!xlu_cfg_get_string (config, "kernel", &buf, 0))
-            fprintf(stderr, "WARNING: ignoring \"kernel\" directive for HVM guest. "
-                    "Use \"firmware_override\" instead if you really want a non-default firmware\n");
+        if (!strcmp(libxl_basename(b_info->kernel), "hvmloader")) {
+            fprintf(stderr, "WARNING: you seem to be using \"kernel\" "
+                    "directive to override HVM guest firmware. Ignore "
+                    "that. Use \"firmware_override\" instead if you "
+                    "really want a non-default firmware\n");
+            b_info->kernel = NULL;
+        }
 
         xlu_cfg_replace_string (config, "firmware_override",
                                 &b_info->u.hvm.firmware, 0);
@@ -1000,26 +1031,8 @@  static void parse_config_data(const char *config_source,
         break;
     case LIBXL_DOMAIN_TYPE_PV:
     {
-        char *cmdline = NULL;
-        const char *root = NULL, *extra = "";
-
         xlu_cfg_replace_string (config, "kernel", &b_info->u.pv.kernel, 0);
 
-        xlu_cfg_get_string (config, "root", &root, 0);
-        xlu_cfg_get_string (config, "extra", &extra, 0);
-
-        if (root) {
-            if (asprintf(&cmdline, "root=%s %s", root, extra) == -1)
-                cmdline = NULL;
-        } else {
-            cmdline = strdup(extra);
-        }
-
-        if ((root || extra) && !cmdline) {
-            fprintf(stderr, "Failed to allocate memory for cmdline\n");
-            exit(1);
-        }
-
         xlu_cfg_replace_string (config, "bootloader", &b_info->u.pv.bootloader, 0);
         switch (xlu_cfg_get_list_as_string_list(config, "bootloader_args",
                                       &b_info->u.pv.bootloader_args, 1))
@@ -1047,7 +1060,7 @@  static void parse_config_data(const char *config_source,
             exit(1);
         }
 
-        b_info->u.pv.cmdline = cmdline;
+        b_info->u.pv.cmdline = parse_cmdline(config);
         xlu_cfg_replace_string (config, "ramdisk", &b_info->u.pv.ramdisk, 0);
         break;
     }