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pve-qemu-qoup/debian/patches/pve/0040-PVE-Migrate-dirty-bitmap-state-via-savevm.patch
Fiona Ebner 5b15e2ecaf update submodule and patches to 7.1.0 
Notable changes:
* The only big change is the switch to using a custom QIOChannel for
  savevm-async, because the previously used QEMUFileOps was dropped.

  Changes to the current implementation:

  * Switch to vector based methods as required for an IO channel. For
    short reads the passed-in IO vector is stuffed with zeroes at the
    end, just to be sure.

  * For reading: The documentation in include/io/channel.h states that
    at least one byte should be read, so also error out when whe are
    at the very end instead of returning 0.

  * For reading: Fix off-by-one error when request goes beyond end.

    The wrong code piece was:
    if ((pos + size) > maxlen) {
        size = maxlen - pos - 1;
    }

    Previously, the last byte would not be read. It's actually
    possible to get a snapshot .raw file that has content all the way
    up the final 512 byte (= BDRV_SECTOR_SIZE) boundary without any
    trailing zero bytes (I wrote a script to do it).

    Luckily, it didn't cause a real issue, because qemu_loadvm_state()
    is not interested in the final (i.e. QEMU_VM_VMDESCRIPTION)
    section. The buffer for reading it is simply freed up afterwards
    and the function will assume that it read the whole section, even
    if that's not the case.

  * For writing: Make use of the generated blk_pwritev() wrapper
    instead of manually wrapping the coroutine to simplify and save a
    few lines.

* Adapt to changed interfaces for blk_{pread,pwrite}:
  * a9262f551e ("block: Change blk_{pread,pwrite}() param order")
  * 3b35d4542c ("block: Add a 'flags' param to blk_pread()")
  * bf5b16fa40 ("block: Make blk_{pread,pwrite}() return 0 on success")
  Those changes especially affected the qemu-img dd patches, because
  the context also changed, but also some of our block drivers used
  the functions.

* Drop qemu-common.h include: it got renamed after essentially
  everything was moved to other headers. The only remaining user I
  could find for things dropped from the header between 7.0 and 7.1
  was qemu_get_vm_name() in the iscsi-initiatorname patch, but it
  already includes the header to which the function was moved.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
2022-10-14 14:52:29 +02:00

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Stefan Reiter <s.reiter@proxmox.com>
Date: Thu, 22 Oct 2020 17:34:18 +0200
Subject: [PATCH] PVE: Migrate dirty bitmap state via savevm
QEMU provides 'savevm' registrations as a mechanism for arbitrary state
to be migrated along with a VM. Use this to send a serialized version of
dirty bitmap state data from proxmox-backup-qemu, and restore it on the
target node.
Also add a flag to query-proxmox-support so qemu-server can determine if
safe migration is possible and makes sense.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
---
include/migration/misc.h | 3 ++
migration/meson.build | 2 +
migration/migration.c | 1 +
migration/pbs-state.c | 106 +++++++++++++++++++++++++++++++++++++++
pve-backup.c | 1 +
qapi/block-core.json | 6 +++
6 files changed, 119 insertions(+)
create mode 100644 migration/pbs-state.c
diff --git a/include/migration/misc.h b/include/migration/misc.h
index 465906710d..4f0aeceb6f 100644
--- a/include/migration/misc.h
+++ b/include/migration/misc.h
@@ -75,4 +75,7 @@ bool migration_in_bg_snapshot(void);
/* migration/block-dirty-bitmap.c */
void dirty_bitmap_mig_init(void);
+/* migration/pbs-state.c */
+void pbs_state_mig_init(void);
+
#endif
diff --git a/migration/meson.build b/migration/meson.build
index 0842d00cd2..d012f4d8d3 100644
--- a/migration/meson.build
+++ b/migration/meson.build
@@ -6,8 +6,10 @@ migration_files = files(
'vmstate.c',
'qemu-file.c',
'yank_functions.c',
+ 'pbs-state.c',
)
softmmu_ss.add(migration_files)
+softmmu_ss.add(libproxmox_backup_qemu)
softmmu_ss.add(files(
'block-dirty-bitmap.c',
diff --git a/migration/migration.c b/migration/migration.c
index bb8bbddfe4..8109e468eb 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -229,6 +229,7 @@ void migration_object_init(void)
blk_mig_init();
ram_mig_init();
dirty_bitmap_mig_init();
+ pbs_state_mig_init();
}
void migration_cancel(const Error *error)
diff --git a/migration/pbs-state.c b/migration/pbs-state.c
new file mode 100644
index 0000000000..29f2b3860d
--- /dev/null
+++ b/migration/pbs-state.c
@@ -0,0 +1,106 @@
+/*
+ * PBS (dirty-bitmap) state migration
+ */
+
+#include "qemu/osdep.h"
+#include "migration/misc.h"
+#include "qemu-file.h"
+#include "migration/vmstate.h"
+#include "migration/register.h"
+#include "proxmox-backup-qemu.h"
+
+typedef struct PBSState {
+ bool active;
+} PBSState;
+
+/* state is accessed via this static variable directly, 'opaque' is NULL */
+static PBSState pbs_state;
+
+static void pbs_state_save_pending(QEMUFile *f, void *opaque,
+ uint64_t max_size,
+ uint64_t *res_precopy_only,
+ uint64_t *res_compatible,
+ uint64_t *res_postcopy_only)
+{
+ /* we send everything in save_setup, so nothing is ever pending */
+}
+
+/* receive PBS state via f and deserialize, called on target */
+static int pbs_state_load(QEMUFile *f, void *opaque, int version_id)
+{
+ /* safe cast, we cannot migrate to target with less bits than source */
+ size_t buf_size = (size_t)qemu_get_be64(f);
+
+ uint8_t *buf = (uint8_t *)malloc(buf_size);
+ size_t read = qemu_get_buffer(f, buf, buf_size);
+
+ if (read < buf_size) {
+ fprintf(stderr, "error receiving PBS state: not enough data\n");
+ return -EIO;
+ }
+
+ proxmox_import_state(buf, buf_size);
+
+ free(buf);
+ return 0;
+}
+
+/* serialize PBS state and send to target via f, called on source */
+static int pbs_state_save_setup(QEMUFile *f, void *opaque)
+{
+ size_t buf_size;
+ uint8_t *buf = proxmox_export_state(&buf_size);
+
+ /* LV encoding */
+ qemu_put_be64(f, buf_size);
+ qemu_put_buffer(f, buf, buf_size);
+
+ proxmox_free_state_buf(buf);
+ pbs_state.active = false;
+ return 0;
+}
+
+static bool pbs_state_is_active(void *opaque)
+{
+ /* we need to return active exactly once, else .save_setup is never called,
+ * but if we'd just return true the migration doesn't make progress since
+ * it'd be waiting for us */
+ return pbs_state.active;
+}
+
+static bool pbs_state_is_active_iterate(void *opaque)
+{
+ /* we don't iterate, everything is sent in save_setup */
+ return pbs_state_is_active(opaque);
+}
+
+static bool pbs_state_has_postcopy(void *opaque)
+{
+ /* PBS state can't change during a migration (since that's blocking any
+ * potential backups), so we can copy everything before the VM is stopped */
+ return false;
+}
+
+static void pbs_state_save_cleanup(void *opaque)
+{
+ /* reset active after migration succeeds or fails */
+ pbs_state.active = false;
+}
+
+static SaveVMHandlers savevm_pbs_state_handlers = {
+ .save_setup = pbs_state_save_setup,
+ .has_postcopy = pbs_state_has_postcopy,
+ .save_live_pending = pbs_state_save_pending,
+ .is_active_iterate = pbs_state_is_active_iterate,
+ .load_state = pbs_state_load,
+ .is_active = pbs_state_is_active,
+ .save_cleanup = pbs_state_save_cleanup,
+};
+
+void pbs_state_mig_init(void)
+{
+ pbs_state.active = true;
+ register_savevm_live("pbs-state", 0, 1,
+ &savevm_pbs_state_handlers,
+ NULL);
+}
diff --git a/pve-backup.c b/pve-backup.c
index 6f05796fad..5fa3cc1352 100644
--- a/pve-backup.c
+++ b/pve-backup.c
@@ -1132,6 +1132,7 @@ ProxmoxSupportStatus *qmp_query_proxmox_support(Error **errp)
ret->pbs_library_version = g_strdup(proxmox_backup_qemu_version());
ret->pbs_dirty_bitmap = true;
ret->pbs_dirty_bitmap_savevm = true;
+ ret->pbs_dirty_bitmap_migration = true;
ret->query_bitmap_info = true;
return ret;
}
diff --git a/qapi/block-core.json b/qapi/block-core.json
index cb17d00fe0..bd978ea562 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -879,6 +879,11 @@
# @pbs-dirty-bitmap-savevm: True if 'dirty-bitmaps' migration capability can
# safely be set for savevm-async.
#
+# @pbs-dirty-bitmap-migration: True if safe migration of dirty-bitmaps including
+# PBS state is supported. Enabling 'dirty-bitmaps'
+# migration cap if this is false/unset may lead
+# to crashes on migration!
+#
# @pbs-library-version: Running version of libproxmox-backup-qemu0 library.
#
##
@@ -886,6 +891,7 @@
'data': { 'pbs-dirty-bitmap': 'bool',
'query-bitmap-info': 'bool',
'pbs-dirty-bitmap-savevm': 'bool',
+ 'pbs-dirty-bitmap-migration': 'bool',
'pbs-library-version': 'str' } }
##
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