xen-blkfront: handle Xen major numbers other than XENVBD

This patch makes sure blkfront handles correctly virtual device numbers
corresponding to Xen emulated IDE and SCSI disks: in those cases
blkfront translates the major number to XENVBD and the minor number to a
low xvd minor.

Note: this behaviour is different from what old xenlinux PV guests used
to do: they used to steal an IDE or SCSI major number and use it
instead.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>

2 files changed, 95 insertions, 5 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index d7aa39e349a6..64d9c6dfc634 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -120,6 +120,10 @@ static DEFINE_SPINLOCK(minor_lock);
 #define EXTENDED (1<<EXT_SHIFT)
 #define VDEV_IS_EXTENDED(dev) ((dev)&(EXTENDED))
 #define BLKIF_MINOR_EXT(dev) ((dev)&(~EXTENDED))
+#define EMULATED_HD_DISK_MINOR_OFFSET (0)
+#define EMULATED_HD_DISK_NAME_OFFSET (EMULATED_HD_DISK_MINOR_OFFSET / 256)
+#define EMULATED_SD_DISK_MINOR_OFFSET (EMULATED_HD_DISK_MINOR_OFFSET + (4 * 16))
+#define EMULATED_SD_DISK_NAME_OFFSET (EMULATED_HD_DISK_NAME_OFFSET + 4)
 
 #define DEV_NAME        "xvd"   /* name in /dev */
 
@@ -434,6 +438,65 @@ static void xlvbd_flush(struct blkfront_info *info)
                info->feature_flush ? "enabled" : "disabled");
 }
 
+static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
+{
+        int major;
+        major = BLKIF_MAJOR(vdevice);
+        *minor = BLKIF_MINOR(vdevice);
+        switch (major) {
+                case XEN_IDE0_MAJOR:
+                        *offset = (*minor / 64) + EMULATED_HD_DISK_NAME_OFFSET;
+                        *minor = ((*minor / 64) * PARTS_PER_DISK) +
+                                EMULATED_HD_DISK_MINOR_OFFSET;
+                        break;
+                case XEN_IDE1_MAJOR:
+                        *offset = (*minor / 64) + 2 + EMULATED_HD_DISK_NAME_OFFSET;
+                        *minor = (((*minor / 64) + 2) * PARTS_PER_DISK) +
+                                EMULATED_HD_DISK_MINOR_OFFSET;
+                        break;
+                case XEN_SCSI_DISK0_MAJOR:
+                        *offset = (*minor / PARTS_PER_DISK) + EMULATED_SD_DISK_NAME_OFFSET;
+                        *minor = *minor + EMULATED_SD_DISK_MINOR_OFFSET;
+                        break;
+                case XEN_SCSI_DISK1_MAJOR:
+                case XEN_SCSI_DISK2_MAJOR:
+                case XEN_SCSI_DISK3_MAJOR:
+                case XEN_SCSI_DISK4_MAJOR:
+                case XEN_SCSI_DISK5_MAJOR:
+                case XEN_SCSI_DISK6_MAJOR:
+                case XEN_SCSI_DISK7_MAJOR:
+                        *offset = (*minor / PARTS_PER_DISK) + 
+                                ((major - XEN_SCSI_DISK1_MAJOR + 1) * 16) +
+                                EMULATED_SD_DISK_NAME_OFFSET;
+                        *minor = *minor +
+                                ((major - XEN_SCSI_DISK1_MAJOR + 1) * 16 * PARTS_PER_DISK) +
+                                EMULATED_SD_DISK_MINOR_OFFSET;
+                        break;
+                case XEN_SCSI_DISK8_MAJOR:
+                case XEN_SCSI_DISK9_MAJOR:
+                case XEN_SCSI_DISK10_MAJOR:
+                case XEN_SCSI_DISK11_MAJOR:
+                case XEN_SCSI_DISK12_MAJOR:
+                case XEN_SCSI_DISK13_MAJOR:
+                case XEN_SCSI_DISK14_MAJOR:
+                case XEN_SCSI_DISK15_MAJOR:
+                        *offset = (*minor / PARTS_PER_DISK) + 
+                                ((major - XEN_SCSI_DISK8_MAJOR + 8) * 16) +
+                                EMULATED_SD_DISK_NAME_OFFSET;
+                        *minor = *minor +
+                                ((major - XEN_SCSI_DISK8_MAJOR + 8) * 16 * PARTS_PER_DISK) +
+                                EMULATED_SD_DISK_MINOR_OFFSET;
+                        break;
+                case XENVBD_MAJOR:
+                        *offset = *minor / PARTS_PER_DISK;
+                        break;
+                default:
+                        printk(KERN_WARNING "blkfront: your disk configuration is "
+                                        "incorrect, please use an xvd device instead\n");
+                        return -ENODEV;
+        }
+        return 0;
+}
 
 static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
                                struct blkfront_info *info,
@@ -441,7 +504,7 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
 {
         struct gendisk *gd;
         int nr_minors = 1;
-        int err = -ENODEV;
+        int err;
         unsigned int offset;
         int minor;
         int nr_parts;
@@ -456,12 +519,20 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
         }
 
         if (!VDEV_IS_EXTENDED(info->vdevice)) {
-                minor = BLKIF_MINOR(info->vdevice);
-                nr_parts = PARTS_PER_DISK;
+                err = xen_translate_vdev(info->vdevice, &minor, &offset);
+                if (err)
+                        return err;             
+                nr_parts = PARTS_PER_DISK;
         } else {
                 minor = BLKIF_MINOR_EXT(info->vdevice);
                 nr_parts = PARTS_PER_EXT_DISK;
+                offset = minor / nr_parts;
+                if (xen_hvm_domain() && offset <= EMULATED_HD_DISK_NAME_OFFSET + 4)
+                        printk(KERN_WARNING "blkfront: vdevice 0x%x might conflict with "
+                                        "emulated IDE disks,\n\t choose an xvd device name"
+                                        "from xvde on\n", info->vdevice);
         }
+        err = -ENODEV;
 
         if ((minor % nr_parts) == 0)
                 nr_minors = nr_parts;
@@ -475,8 +546,6 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
         if (gd == NULL)
                 goto release;
 
-        offset = minor / nr_parts;
-
         if (nr_minors > 1) {
                 if (offset < 26)
                         sprintf(gd->disk_name, "%s%c", DEV_NAME, 'a' + offset);
diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
index c2d1fa4dc1ee..68dd2b49635c 100644
--- a/include/xen/interface/io/blkif.h
+++ b/include/xen/interface/io/blkif.h
@@ -91,4 +91,25 @@ DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
 #define VDISK_REMOVABLE    0x2
 #define VDISK_READONLY     0x4
 
+/* Xen-defined major numbers for virtual disks, they look strangely
+ * familiar */
+#define XEN_IDE0_MAJOR  3
+#define XEN_IDE1_MAJOR  22
+#define XEN_SCSI_DISK0_MAJOR    8
+#define XEN_SCSI_DISK1_MAJOR    65
+#define XEN_SCSI_DISK2_MAJOR    66
+#define XEN_SCSI_DISK3_MAJOR    67
+#define XEN_SCSI_DISK4_MAJOR    68
+#define XEN_SCSI_DISK5_MAJOR    69
+#define XEN_SCSI_DISK6_MAJOR    70
+#define XEN_SCSI_DISK7_MAJOR    71
+#define XEN_SCSI_DISK8_MAJOR    128
+#define XEN_SCSI_DISK9_MAJOR    129
+#define XEN_SCSI_DISK10_MAJOR   130
+#define XEN_SCSI_DISK11_MAJOR   131
+#define XEN_SCSI_DISK12_MAJOR   132
+#define XEN_SCSI_DISK13_MAJOR   133
+#define XEN_SCSI_DISK14_MAJOR   134
+#define XEN_SCSI_DISK15_MAJOR   135
+
 #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */