libxl: Rearrange qemu upstream disk argument code

Reorganize the qemuu disk argument code to make a clean separation
between finding a file to use, and constructing the parameters:

* Rename pdev_path to target_path

* Only use qemu_disk_format_string() in circumstances where qemu may
be interpreting the disk (i.e., backend==QDISK).  In all other cases,
it should use RAW.

* Share as much as possible between the is_cdrom path and the normal
path.

This is mainly prep for sharing the local path finder with the
bootloader; but it does allow cdroms to use any backend that a normal
disk can use. Previously this was limited to RAW files or things that
qemu could handle directly; as of this changeset, it now includes tap
disks; and in future changesets it will include backends with custom
block scripts.

NB that this retains an existing bug, that disks with custom block
scripts or non-dom0 backends will have the bogus pdev_path passed in
to qemu, most likely resulting in qemu exiting with an error.  This
will be fixed in follow-up patches.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>
Tested-by: George Dunlap <george.dunlap@citrix.com>

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 3522fbff405ad466e2a8941142e35916c29aef1f..c11e9b811ea5b6654a80a7925fee4f95765567e6 100644 (file)
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -761,7 +761,7 @@ enum {
     LIBXL__COLO_SECONDARY,
 };
 
-static char *qemu_disk_scsi_drive_string(libxl__gc *gc, const char *pdev_path,
+static char *qemu_disk_scsi_drive_string(libxl__gc *gc, const char *target_path,
                                          int unit, const char *format,
                                          const libxl_device_disk *disk,
                                          int colo_mode)
@@ -775,14 +775,14 @@ static char *qemu_disk_scsi_drive_string(libxl__gc *gc, const char *pdev_path,
     case LIBXL__COLO_NONE:
         drive = libxl__sprintf
             (gc, "file=%s,if=scsi,bus=0,unit=%d,format=%s,cache=writeback",
-             pdev_path, unit, format);
+             target_path, unit, format);
         break;
     case LIBXL__COLO_PRIMARY:
         /*
          * primary:
          *  -dirve if=scsi,bus=0,unit=x,cache=writeback,driver=quorum,\
          *  id=exportname,\
-         *  children.0.file.filename=pdev_path,\
+         *  children.0.file.filename=target_path,\
          *  children.0.driver=format,\
          *  read-pattern=fifo,\
          *  vote-threshold=1
@@ -794,7 +794,7 @@ static char *qemu_disk_scsi_drive_string(libxl__gc *gc, const char *pdev_path,
             "children.0.driver=%s,"
             "read-pattern=fifo,"
             "vote-threshold=1",
-            unit, exportname, pdev_path, format);
+            unit, exportname, target_path, format);
         break;
     case LIBXL__COLO_SECONDARY:
         /*
@@ -823,7 +823,7 @@ static char *qemu_disk_scsi_drive_string(libxl__gc *gc, const char *pdev_path,
     return drive;
 }
 
-static char *qemu_disk_ide_drive_string(libxl__gc *gc, const char *pdev_path,
+static char *qemu_disk_ide_drive_string(libxl__gc *gc, const char *target_path,
                                         int unit, const char *format,
                                         const libxl_device_disk *disk,
                                         int colo_mode)
@@ -837,14 +837,14 @@ static char *qemu_disk_ide_drive_string(libxl__gc *gc, const char *pdev_path,
     case LIBXL__COLO_NONE:
         drive = GCSPRINTF
             ("file=%s,if=ide,index=%d,media=disk,format=%s,cache=writeback",
-             pdev_path, unit, format);
+             target_path, unit, format);
         break;
     case LIBXL__COLO_PRIMARY:
         /*
          * primary:
          *  -dirve if=ide,index=x,media=disk,cache=writeback,driver=quorum,\
          *  id=exportname,\
-         *  children.0.file.filename=pdev_path,\
+         *  children.0.file.filename=target_path,\
          *  children.0.driver=format,\
          *  read-pattern=fifo,\
          *  vote-threshold=1
@@ -856,7 +856,7 @@ static char *qemu_disk_ide_drive_string(libxl__gc *gc, const char *pdev_path,
             "children.0.driver=%s,"
             "read-pattern=fifo,"
             "vote-threshold=1",
-             unit, exportname, pdev_path, format);
+             unit, exportname, target_path, format);
         break;
     case LIBXL__COLO_SECONDARY:
         /*
@@ -1305,9 +1305,9 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
             int disk, part;
             int dev_number =
                 libxl__device_disk_dev_number(disks[i].vdev, &disk, &part);
-            const char *format = qemu_disk_format_string(disks[i].format);
+            const char *format;
             char *drive;
-            const char *pdev_path;
+            const char *target_path;
             int colo_mode;
 
             if (dev_number == -1) {
@@ -1316,22 +1316,22 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
                 continue;
             }
 
-            if (disks[i].is_cdrom) {
-                if (disks[i].format == LIBXL_DISK_FORMAT_EMPTY)
-                    drive = libxl__sprintf
-                        (gc, "if=ide,index=%d,readonly=%s,media=cdrom,cache=writeback,id=ide-%i",
-                         disk, disks[i].readwrite ? "off" : "on", dev_number);
-                else
-                    drive = libxl__sprintf
-                        (gc, "file=%s,if=ide,index=%d,readonly=%s,media=cdrom,format=%s,cache=writeback,id=ide-%i",
-                         disks[i].pdev_path, disk, disks[i].readwrite ? "off" : "on", format, dev_number);
-            } else {
-                if (disks[i].format == LIBXL_DISK_FORMAT_EMPTY) {
+            /* 
+             * If qemu isn't doing the interpreting, the parameter is
+             * always raw
+             */
+            if (disks[i].backend == LIBXL_DISK_BACKEND_QDISK)
+                format = qemu_disk_format_string(disks[i].format);
+            else
+                format = qemu_disk_format_string(LIBXL_DISK_FORMAT_RAW);
+
+            if (disks[i].format == LIBXL_DISK_FORMAT_EMPTY) {
+                if (!disks[i].is_cdrom) {
                     LOG(WARN, "cannot support"" empty disk format for %s",
                         disks[i].vdev);
                     continue;
                 }
-
+            } else {
                 if (format == NULL) {
                     LOG(WARN,
                         "unable to determine"" disk image format %s",
@@ -1339,14 +1339,22 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
                     continue;
                 }
 
-                if (disks[i].backend == LIBXL_DISK_BACKEND_TAP) {
-                    format = qemu_disk_format_string(LIBXL_DISK_FORMAT_RAW);
-                    pdev_path = libxl__blktap_devpath(gc, disks[i].pdev_path,
-                                                      disks[i].format);
-                } else {
-                    pdev_path = disks[i].pdev_path;
-                }
+                if (disks[i].backend == LIBXL_DISK_BACKEND_TAP)
+                    target_path = libxl__blktap_devpath(gc, disks[i].pdev_path,
+                                                        disks[i].format);
+                else     
+                    target_path = disks[i].pdev_path;
+            }
 
+            if (disks[i].is_cdrom) {
+                drive = libxl__sprintf(gc,
+                         "if=ide,index=%d,readonly=%s,media=cdrom,cache=writeback,id=ide-%i",
+                         disk, disks[i].readwrite ? "off" : "on", dev_number);
+
+                if (target_path)
+                    drive = libxl__sprintf(gc, "%s,file=%s,format=%s",
+                                           drive, target_path, format);
+            } else {
                 /*
                  * Explicit sd disks are passed through as is.
                  *
@@ -1367,12 +1375,12 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
                     if (colo_mode == LIBXL__COLO_SECONDARY) {
                         drive = libxl__sprintf
                             (gc, "if=none,driver=%s,file=%s,id=%s",
-                             format, pdev_path, disks[i].colo_export);
+                             format, target_path, disks[i].colo_export);
 
                         flexarray_append(dm_args, "-drive");
                         flexarray_append(dm_args, drive);
                     }
-                    drive = qemu_disk_scsi_drive_string(gc, pdev_path, disk,
+                    drive = qemu_disk_scsi_drive_string(gc, target_path, disk,
                                                         format,
                                                         &disks[i],
                                                         colo_mode);
@@ -1389,7 +1397,7 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
                     }
                     flexarray_vappend(dm_args, "-drive",
                         GCSPRINTF("file=%s,if=none,id=ahcidisk-%d,format=%s,cache=writeback",
-                        pdev_path, disk, format),
+                        target_path, disk, format),
                         "-device", GCSPRINTF("ide-hd,bus=ahci0.%d,unit=0,drive=ahcidisk-%d",
                         disk, disk), NULL);
                     continue;
@@ -1401,12 +1409,12 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
                     if (colo_mode == LIBXL__COLO_SECONDARY) {
                         drive = libxl__sprintf
                             (gc, "if=none,driver=%s,file=%s,id=%s",
-                             format, pdev_path, disks[i].colo_export);
+                             format, target_path, disks[i].colo_export);
 
                         flexarray_append(dm_args, "-drive");
                         flexarray_append(dm_args, drive);
                     }
-                    drive = qemu_disk_ide_drive_string(gc, pdev_path, disk,
+                    drive = qemu_disk_ide_drive_string(gc, target_path, disk,
                                                        format,
                                                        &disks[i],
                                                        colo_mode);