libxl: add function to attach/detach a disk to/from the local VM

Useful if you need to read a guest filesystem (e.g. pygrub).

I'm not overly thrilled with the implementation WRT tap interfaces,
particularly WRT to detach. I was unable to find a way to get at the
paramters necessary to call tap_ctl_destroy so I assumed for now it
that is OK to assume that the tap device is going to be wanted for the
actual domain at some point in the immediate future and hence there is
no pressing need to destroy it.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index bd39454ca7ab642cc1abc06f3ba8fdd3e8f953e8..8d05d6faf7e2f35c066bb0a8c2f58092028b60c4 100644 (file)
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -1425,6 +1425,48 @@ int libxl_device_disk_del(struct libxl_ctx *ctx,
     return libxl_device_del(ctx, &device, wait);
 }
 
+const char * libxl_device_disk_local_attach(struct libxl_ctx *ctx, libxl_device_disk *disk)
+{
+    char *dev = NULL;
+    int phystype = disk->phystype;
+    switch (phystype) {
+        case PHYSTYPE_PHY: {
+            fprintf(stderr, "attaching PHY disk %s to domain 0\n", disk->physpath);
+            dev = disk->physpath;
+            break;
+        }
+        case PHYSTYPE_FILE:
+            /* let's pretend is tap:aio for the moment */
+            phystype = PHYSTYPE_AIO;
+        case PHYSTYPE_AIO: case PHYSTYPE_QCOW: case PHYSTYPE_QCOW2: case PHYSTYPE_VHD: {
+            const char *msg;
+            if (!tap_ctl_check(&msg)) {
+                const char *type = device_disk_string_of_phystype(phystype);
+                dev = get_blktap2_device(ctx, disk->physpath, type);
+                if (!dev)
+                    dev = make_blktap2_device(ctx, disk->physpath, type);
+            }
+            break;
+        }
+        default:
+            XL_LOG(ctx, XL_LOG_ERROR, "unrecognized disk physical type: %d\n", phystype);
+            break;
+    }
+    return dev;
+}
+
+int libxl_device_disk_local_detach(struct libxl_ctx *ctx, libxl_device_disk *disk)
+{
+    /* Nothing to do for PHYSTYPE_PHY. */
+
+    /*
+     * For other device types assume that the blktap2 process is
+     * needed by the soon to be started domain and do nothing.
+     */
+
+    return 0;
+}
+
 /******************************************************************************/
 int libxl_device_nic_add(struct libxl_ctx *ctx, uint32_t domid, libxl_device_nic *nic)
 {

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index e58e9a5238ed5415fbc107ebaaa5a854313f4798..2998d6a30c8c7190e589d2f6b1cfc3cd555744ff 100644 (file)
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -423,6 +423,12 @@ int libxl_device_disk_getinfo(struct libxl_ctx *ctx, uint32_t domid,
                               libxl_device_disk *disk, libxl_diskinfo *diskinfo);
 int libxl_cdrom_insert(struct libxl_ctx *ctx, uint32_t domid, libxl_device_disk *disk);
 
+/*
+ * Make a disk available in this domain. Returns path to a device.
+ */
+const char * libxl_device_disk_local_attach(struct libxl_ctx *ctx, libxl_device_disk *disk);
+int libxl_device_disk_local_detach(struct libxl_ctx *ctx, libxl_device_disk *disk);
+
 typedef struct {
     char *backend;
     uint32_t backend_id;