libxl: Add AHCI support for upstream qemu

Usage:
hdtype=ide|ahci (default=ide)

If hdtype=ahci adds ich9 disk controller in ahci mode and uses it with
upstream qemu to emulate disks instead of ide.
It doesn't support cdroms which still using ide (cdroms will use
"-device ide-cd" as new qemu parameter)
Ahci requires new qemu parameter but for now other emulated disks cases
remains with old ones (I did it in other patch, not needed by this one)
I did it as libxl parameter disabled by default to avoid possible
problems:
- with save/restore/migration (restoring with ahci a domU that was with
ide instead)
- windows < 8 without pv drivers (a registry key change is needed for
AHCI<->IDE change FWIK to avoid possible blue screen)
- windows XP or older that many not support ahci by default.
Setting AHCI with libxl parameter and default to disabled seems the best
solution.
AHCI increase hvm domUs boot performance. On linux hvm domU I saw up to
only 20% of the previous total boot time, whereas boot time decrease a
lot on W7 domUs for most of boots I have done. Small difference in boot
time compared to ide mode on W8 and newer (probably other xen
improvements or fixes are needed not ahci related)

Signed-off-by: Fabio Fantoni <fabio.fantoni@m2r.biz>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
[ ijc -- adjust name of LIBXL_HAVE #define as discussed on list,
         fixup pod syntax in xl.cfg.pod.5 ]

docs/man/xl.cfg.pod.5

@@ -882,6 +882,20 @@ default is B<cd>.
 
 =back
 
+=head3 Emulated disk controller type
+
+=over 4
+
+=item B<hdtype="STRING">
+
+Select the hd disk type (ide|ahci).
+If hdtype=ahci adds ich9 disk controller in AHCI mode and uses it with
+upstream qemu to emulate disks instead of IDE. It decreases boot time
+but may not be supported by default in Windows xp and older Windows.
+The default is ide.
+
+=back
+
 =head3 Paging
 
 The following options control the mechanisms used to virtualise guest

docs/misc/vbd-interface.txt

@@ -3,18 +3,20 @@ Xen guest interface
 
 A Xen guest can be provided with block devices.  These are always
 provided as Xen VBDs; for HVM guests they may also be provided as
-emulated IDE or SCSI disks.
+emulated IDE, AHCI or SCSI disks.
 
 The abstract interface involves specifying, for each block device:
 
  * Nominal disk type: Xen virtual disk (aka xvd*, the default); SCSI
-   (sd*); IDE (hd*).
+   (sd*); IDE or AHCI (hd*).
 
    For HVM guests, each whole-disk hd* and and sd* device is made
    available _both_ via emulated IDE resp. SCSI controller, _and_ as a
    Xen VBD.  The HVM guest is entitled to assume that the IDE or SCSI
    disks available via the emulated IDE controller target the same
    underlying devices as the corresponding Xen VBD (ie, multipath).
+   In hd* case with hdtype=ahci, disk will be AHCI via emulated
+   ich9 disk controller.
 
    For PV guests every device is made available to the guest only as a
    Xen VBD.  For these domains the type is advisory, for use by the

tools/libxl/libxl.h

@@ -595,6 +595,14 @@ typedef struct libxl__ctx libxl_ctx;
  */
 #define LIBXL_HAVE_SPICE_STREAMINGVIDEO 1
 
+/*
+ * LIBXL_HAVE_HVM_HDTYPE
+ *
+ * If defined, then the u.hvm structure will contain a enum type
+ * hdtype.
+ */
+#define LIBXL_HAVE_HVM_HDTYPE 1
+
 /*
  * LIBXL_HAVE_DOMAIN_CREATE_RESTORE_PARAMS 1
  *

tools/libxl/libxl_create.c

@@ -195,6 +195,9 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
         if (!b_info->u.hvm.vga.kind)
             b_info->u.hvm.vga.kind = LIBXL_VGA_INTERFACE_TYPE_CIRRUS;
 
+        if (!b_info->u.hvm.hdtype)
+            b_info->u.hvm.hdtype = LIBXL_HDTYPE_IDE;
+
         switch (b_info->device_model_version) {
         case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL:
             switch (b_info->u.hvm.vga.kind) {

tools/libxl/libxl_dm.c

@@ -818,6 +818,8 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
     flexarray_append(dm_args, libxl__sprintf(gc, "%"PRId64, ram_size));
 
     if (b_info->type == LIBXL_DOMAIN_TYPE_HVM) {
+        if (b_info->u.hvm.hdtype == LIBXL_HDTYPE_AHCI)
+            flexarray_append_pair(dm_args, "-device", "ahci,id=ahci0");
         for (i = 0; i < num_disks; i++) {
             int disk, part;
             int dev_number =
@@ -872,7 +874,14 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
                     drive = libxl__sprintf
                         (gc, "file=%s,if=scsi,bus=0,unit=%d,format=%s,cache=writeback",
                          pdev_path, disk, format);
-                else if (disk < 4)
+                else if (disk < 6 && b_info->u.hvm.hdtype == LIBXL_HDTYPE_AHCI) {
+                    flexarray_vappend(dm_args, "-drive",
+                        GCSPRINTF("file=%s,if=none,id=ahcidisk-%d,format=%s,cache=writeback",
+                        pdev_path, disk, format),
+                        "-device", GCSPRINTF("ide-hd,bus=ahci0.%d,unit=0,drive=ahcidisk-%d",
+                        disk, disk), NULL);
+                    continue;
+                } else if (disk < 4)
                     drive = libxl__sprintf
                         (gc, "file=%s,if=ide,index=%d,media=disk,format=%s,cache=writeback",
                          pdev_path, disk, format);

tools/libxl/libxl_types.idl

@@ -202,6 +202,11 @@ libxl_viridian_enlightenment = Enumeration("viridian_enlightenment", [
     (3, "reference_tsc"),
     ])
 
+libxl_hdtype = Enumeration("hdtype", [
+    (1, "IDE"),
+    (2, "AHCI"),
+    ], init_val = "LIBXL_HDTYPE_IDE")
+
 #
 # Complex libxl types
 #
@@ -448,6 +453,7 @@ libxl_domain_build_info = Struct("domain_build_info",[
                                        ("nested_hvm",       libxl_defbool),
                                        ("smbios_firmware",  string),
                                        ("acpi_firmware",    string),
+                                       ("hdtype",           libxl_hdtype),
                                        ("nographic",        libxl_defbool),
                                        ("vga",              libxl_vga_interface_info),
                                        ("vnc",              libxl_vnc_info),

tools/libxl/xl_cmdimpl.c

@@ -2154,6 +2154,13 @@ skip_vfb:
             b_info->u.hvm.vga.kind = l ? LIBXL_VGA_INTERFACE_TYPE_STD :
                                          LIBXL_VGA_INTERFACE_TYPE_CIRRUS;
 
+        if (!xlu_cfg_get_string(config, "hdtype", &buf, 0) &&
+            libxl_hdtype_from_string(buf, &b_info->u.hvm.hdtype)) {
+                fprintf(stderr, "ERROR: invalid value \"%s\" for \"hdtype\"\n",
+                    buf);
+                exit (1);
+        }
+
         xlu_cfg_replace_string (config, "keymap", &b_info->u.hvm.keymap, 0);
         xlu_cfg_get_defbool (config, "spice", &b_info->u.hvm.spice.enable, 0);
         if (!xlu_cfg_get_long (config, "spiceport", &l, 0))