[Qemu-devel] [PATCH v8] block/raw-posix.c: Make physical devices usable in QEMU under Mac OS X host

[Programmingkid <programmingkidx@gmail.com>]

Mac OS X can be picky when it comes to allowing the user
to use physical devices in QEMU. Most mounted volumes
appear to be off limits to QEMU. If an issue is detected,
a message is displayed showing the user how to unmount a
volume.

Signed-off-by: John Arbuckle <programmingkidx@gmail.com>

---
 block/raw-posix.c |   98 +++++++++++++++++++++++++++++++++++++++--------------
 1 files changed, 72 insertions(+), 26 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index ccfec1c..d0190c1 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -42,9 +42,8 @@
 #include <IOKit/storage/IOMediaBSDClient.h>
 #include <IOKit/storage/IOMedia.h>
 #include <IOKit/storage/IOCDMedia.h>
-//#include <IOKit/storage/IOCDTypes.h>
 #include <CoreFoundation/CoreFoundation.h>
-#endif
+#endif /* (__APPLE__) && (__MACH__) */
 
 #ifdef __sun__
 #define _POSIX_PTHREAD_SEMANTICS 1
@@ -2033,7 +2032,36 @@ kern_return_t GetBSDPath(io_iterator_t mediaIterator, char *bsdPath,
     return kernResult;
 }
 
-#endif
+/* Sets up a real cdrom for use in QEMU */
+static bool setup_cdrom(char *bsd_path, Error **errp)
+{
+    int index, num_of_test_partitions = 2, fd;
+    char test_partition[MAXPATHLEN];
+    bool partition_found = false;
+
+    /* look for a working partition */
+    for (index = 0; index < num_of_test_partitions; index++) {
+        snprintf(test_partition, sizeof(test_partition), "%ss%d", bsd_path,
+                                                                         index);
+        fd = qemu_open(test_partition, O_RDONLY | O_BINARY | O_LARGEFILE);
+        if (fd >= 0) {
+            partition_found = true;
+            qemu_close(fd);
+            break;
+        }
+    }
+
+    /* if a working partition on the device was not found */
+    if (partition_found == false) {
+        error_setg(errp, "Error: Failed to find a working partition on "
+                                                                     "disc!\n");
+    } else {
+        DPRINTF("Using %s as optical disc\n", test_partition);
+        pstrcpy(bsd_path, MAXPATHLEN, test_partition);
+    }
+    return partition_found;
+}
+#endif /* defined(__APPLE__) && defined(__MACH__) */
 
 static int hdev_probe_device(const char *filename)
 {
@@ -2115,6 +2143,17 @@ static bool hdev_is_sg(BlockDriverState *bs)
     return false;
 }
 
+/* Prints directions on mounting and unmounting a device */
+static void printUnmountingDirections(const char *file_name)
+{
+    error_report("Error: If device %s is mounted on the desktop, unmount"
+                             " it first before using it in QEMU.\n", file_name);
+    error_report("Command to unmount device: diskutil unmountDisk %s\n",
+                                                                     file_name);
+    error_report("Command to mount device: diskutil mountDisk %s\n",
+                                                                     file_name);
+}
+
 static int hdev_open(BlockDriverState *bs, QDict *options, int flags,
                      Error **errp)
 {
@@ -2123,32 +2162,32 @@ static int hdev_open(BlockDriverState *bs, QDict *options, int flags,
     int ret;
 
 #if defined(__APPLE__) && defined(__MACH__)
-    const char *filename = qdict_get_str(options, "filename");
+    const char *file_name = qdict_get_str(options, "filename");
 
-    if (strstart(filename, "/dev/cdrom", NULL)) {
-        kern_return_t kernResult;
+    /* If using a real cdrom */
+    if (strcmp(file_name, "/dev/cdrom") == 0) {
+        char bsd_path[MAXPATHLEN];
         io_iterator_t mediaIterator;
-        char bsdPath[ MAXPATHLEN ];
-        int fd;
-
-        kernResult = FindEjectableCDMedia( &mediaIterator );
-        kernResult = GetBSDPath(mediaIterator, bsdPath, sizeof(bsdPath),
-                                                                        flags);
-        if ( bsdPath[ 0 ] != '\0' ) {
-            strcat(bsdPath,"s0");
-            /* some CDs don't have a partition 0 */
-            fd = qemu_open(bsdPath, O_RDONLY | O_BINARY | O_LARGEFILE);
-            if (fd < 0) {
-                bsdPath[strlen(bsdPath)-1] = '1';
-            } else {
-                qemu_close(fd);
-            }
-            filename = bsdPath;
-            qdict_put(options, "filename", qstring_from_str(filename));
+        FindEjectableCDMedia(&mediaIterator);
+        GetBSDPath(mediaIterator, bsd_path, sizeof(bsd_path), flags);
+        if (mediaIterator) {
+            IOObjectRelease(mediaIterator);
+        }
+
+        /* If a real optical drive was not found */
+        if (bsd_path[0] == '\0') {
+            error_setg(errp, "Error: failed to obtain bsd path for optical"
+                                                                   " drive!\n");
+            return -1;
         }
 
-        if ( mediaIterator )
-            IOObjectRelease( mediaIterator );
+        /* If finding a partition on the cdrom disc failed */
+        if (setup_cdrom(bsd_path, errp) == false) {
+            printUnmountingDirections(bsd_path);
+            return -1;
+        }
+        file_name = bsd_path;
+        qdict_put(options, "filename", qstring_from_str(file_name));
     }
 #endif
 
@@ -2159,9 +2198,16 @@ static int hdev_open(BlockDriverState *bs, QDict *options, int flags,
         if (local_err) {
             error_propagate(errp, local_err);
         }
-        return ret;
     }
 
+#if defined(__APPLE__) && defined(__MACH__)
+    /* if a physical device experienced an error while being opened */
+    if (strncmp(file_name, "/dev/", 5) == 0 && ret != 0) {
+        printUnmountingDirections(file_name);
+        return -1;
+    }
+#endif /* defined(__APPLE__) && defined(__MACH__) */
+
     /* Since this does ioctl the device must be already opened */
     bs->sg = hdev_is_sg(bs);
 
-- 
1.7.5.4