[Qemu-devel] [PATCH v6 8/8] block: allow to skip block driver in selection of one for VM state saving

["Denis V. Lunev" <den@openvz.org>]

Some block drives like PFLASH ones in OVFM setup are not suitable for
VM state saving. Allow option to ban them in this selection.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: Juan Quintela <quintela@redhat.com>
CC: Amit Shah <amit.shah@redhat.com>
---
Changes from v5:
- added to vmstate option to blkdev JSON

 block.c                   |  7 +++++++
 block/snapshot.c          | 10 ++++++++++
 include/block/block_int.h |  3 +++
 qapi/block-core.json      |  5 ++++-
 4 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/block.c b/block.c
index 01655de..08c1db6 100644
--- a/block.c
+++ b/block.c
@@ -895,6 +895,12 @@ static QemuOptsList bdrv_runtime_opts = {
             .type = QEMU_OPT_BOOL,
             .help = "Ignore flush requests",
         },
+        {
+            .name = "vmstate",
+            .type = QEMU_OPT_BOOL,
+            .help = "Allow to to save VM state to this block device",
+            .def_value_str = "on",
+        },
         { /* end of list */ }
     },
 };
@@ -957,6 +963,7 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
     bs->zero_beyond_eof = true;
     open_flags = bdrv_open_flags(bs, flags);
     bs->read_only = !(open_flags & BDRV_O_RDWR);
+    bs->enable_vmstate = qemu_opt_get_bool(opts, "vmstate", true);
 
     if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv, bs->read_only)) {
         error_setg(errp,
diff --git a/block/snapshot.c b/block/snapshot.c
index 237a015..eb73c76 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -498,6 +498,12 @@ BlockDriverState *bdrv_all_find_vmstate_bs(const char *device, Error **errp)
                        device);
             return NULL;
         }
+        if (!bs->enable_vmstate) {
+            error_setg(errp,
+                       "It is not allowed to save VM state to the device '%s'",
+                       device);
+            return NULL;
+        }
 
         ctx = bdrv_get_aio_context(bs);
 
@@ -515,6 +521,10 @@ BlockDriverState *bdrv_all_find_vmstate_bs(const char *device, Error **errp)
     while (not_found && (bs = bdrv_next(bs))) {
         ctx = bdrv_get_aio_context(bs);
 
+        if (!bs->enable_vmstate) {
+            continue;
+        }
+
         aio_context_acquire(ctx);
         not_found = !bdrv_can_snapshot(bs);
         aio_context_release(ctx);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 256609d..a30b576 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -438,6 +438,9 @@ struct BlockDriverState {
     /* do we need to tell the quest if we have a volatile write cache? */
     int enable_write_cache;
 
+    /* allow to save VM state on snapshot here */
+    bool enable_vmstate;
+
     /* the following member gives a name to every node on the bs graph. */
     char node_name[32];
     /* element of the list of named nodes building the graph */
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 0a915ed..d04453f 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1583,6 +1583,8 @@
 #                   statistics, in seconds (default: none) (Since 2.5)
 # @detect-zeroes: #optional detect and optimize zero writes (Since 2.1)
 #                 (default: off)
+# @vmstate: #optional allow to save VM state to this device (Since 2.6)
+#           (default: on)
 #
 # Since: 1.7
 ##
@@ -1599,7 +1601,8 @@
             '*stats-account-invalid': 'bool',
             '*stats-account-failed': 'bool',
             '*stats-intervals': ['int'],
-            '*detect-zeroes': 'BlockdevDetectZeroesOptions' } }
+            '*detect-zeroes': 'BlockdevDetectZeroesOptions',
+            '*vmstate': 'bool' } }
 
 ##
 # @BlockdevOptionsFile
-- 
2.5.0