[Xen-devel] [PATCH v2 5/9] libxl: Rearrange qemu upstream disk argument code

[George Dunlap <george.dunlap@xxxxxxxxxx>]

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@xxxxxxxxxx>
---
Changes since v1:
- Move qemuu disk argument refactoring into a separate patch

CC: Ian Jackson <ian.jackson@xxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
CC: Anthony Perard <anthony.perard@xxxxxxxxxx>
---
 tools/libxl/libxl_dm.c | 61 +++++++++++++++++++++++++++++---------------------
 1 file changed, 35 insertions(+), 26 deletions(-)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 4aca38e..dfcf141 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -1161,9 +1161,9 @@ 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;
 
             if (dev_number == -1) {
                 LOG(WARN, "unable to determine"" disk number for %s",
@@ -1171,22 +1171,22 @@ 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",
@@ -1194,14 +1194,22 @@ 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.
                  *
@@ -1209,9 +1217,10 @@ static int libxl__build_device_model_args_new(libxl__gc 
*gc,
                  * hd[a-d] and ignore the rest.
                  */
                 if (strncmp(disks[i].vdev, "sd", 2) == 0) {
-                    drive = libxl__sprintf
-                        (gc, 
"file=%s,if=scsi,bus=0,unit=%d,format=%s,readonly=%s,cache=writeback",
-                         pdev_path, disk, format, disks[i].readwrite ? "off" : 
"on");
+                    drive = libxl__sprintf(gc,
+                             
"file=%s,if=scsi,bus=0,unit=%d,format=%s,readonly=%s,cache=writeback",
+                             target_path, disk, format,
+                             disks[i].readwrite ? "off" : "on");
                 } else if (strncmp(disks[i].vdev, "xvd", 3) == 0) {
                     /*
                      * Do not add any emulated disk when PV disk are
@@ -1225,7 +1234,7 @@ 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;
@@ -1236,7 +1245,7 @@ static int libxl__build_device_model_args_new(libxl__gc 
*gc,
                     }
                     drive = libxl__sprintf
                         (gc, 
"file=%s,if=ide,index=%d,media=disk,format=%s,cache=writeback",
-                         pdev_path, disk, format);
+                         target_path, disk, format);
                 } else {
                     continue; /* Do not emulate this disk */
                 }
-- 
2.1.4


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