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update submodule and patches to QEMU 8.2.2

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This version includes both the AioContext lock and the block graph
lock, so there might be some deadlocks lurking. It's not possible to
disable the block graph lock like was done in QEMU 8.1, because there
are no changes like the function bdrv_schedule_unref() that require
it. QEMU 9.0 will finally get rid of the AioContext locking.

During live-restore with a VirtIO SCSI drive with iothread there is a
known racy deadlock related to the AioContext lock. Not new [1], but
not sure if more likely now. Should be fixed in QEMU 9.0.

The block graph lock comes with annotations that can be checked by
clang's TSA. This required changes to the block drivers, i.e.
alloc-track, pbs, zeroinit as well as taking the appropriate locks
in pve-backup, savevm-async, vma-reader.

Local variable shadowing is prohibited via a compiler flag now,
required slight adaptation in vma.c.

Major changes only affect alloc-track:

* It is not possible to call a generated co-wrapper like
  bdrv_get_info() while holding the block graph lock exclusively [0],
  which does happen during initialization of alloc-track when the
  backing hd is set and the refresh_limits driver callback is invoked.

  The bdrv_get_info() call to get the cluster size is moved to
  directly after opening the file child in track_open().

  The important thing is that at least the request alignment for the
  write target is used, because then the RMW cycle in bdrv_pwritev
  will gather enough data from the backing file. Partial cluster
  allocations in the target are not a fundamental issue, because the
  driver returns its allocation status based on the bitmap, so any
  other data that maps to the same cluster will still be copied later
  by a stream job (or during writes to that cluster).

* Replacing the node cannot be done in the
  track_co_change_backing_file() callback, because it is a coroutine
  and cannot hold the block graph lock exclusively. So it is moved to
  the stream job itself with the auto-remove option not having an
  effect anymore (qemu-server would always set it anyways).

  In the future, there could either be a special option for the stream
  job, or maybe the upcoming blockdev-replace QMP command can be used.

  Replacing the backing child is actually already done in the stream
  job, so no need to do it in the track_co_change_backing_file()
  callback. It also cannot be called from a coroutine. Looking at the
  implementation in the qcow2 driver, it doesn't seem to be intended
  to change the backing child itself, just update driver-internal
  state.

Other changes:

* alloc-track: Error out early when used without auto-remove. Since
  replacing the node now happens in the stream job, where the option
  cannot be read from (it's internal to the driver), it will always be
  treated as 'on'. Makes sure to have users beside qemu-server notice
  the change (should they even exist). The option can be fully dropped
  in the future while adding a version guard in qemu-server.

* alloc-track: Avoid seemingly superfluous child permission update.
  Doesn't seem necessary nowadays (maybe after commit "alloc-track:
  fix deadlock during drop" where the dropping is not rescheduled and
  delayed anymore or some upstream change). Replacing the block node
  will already update the permissions of the new node (which was the
  file child before). Should there really be some issue, instead of
  having a drop state, this could also be just based off the fact
  whether there is still a backing child.

  Dumping the cumulative (shared) permissions for the BDS with a debug
  print yields the same values after this patch and with QEMU 8.1,
  namely 3 and 5.

* PBS block driver: compile unconditionally. Proxmox VE always needs
  it and something in the build process changed to make it not enabled
  by default. Probably would need to move the build option to meson
  otherwise.

* backup: job unreferencing during cleanup needs to happen outside of
  coroutine, so it was moved to before invoking the clean

* mirror: Cherry-pick stable fix to avoid potential deadlock.

* savevm-async: migrate_init now can fail, so propagate potential
  error.

* savevm-async: compression counters are not accessible outside
  migration/ram-compress now, so drop code that prophylactically set
  it to zero.

[0]: https://lore.kernel.org/qemu-devel/220be383-3b0d-4938-b584-69ad214e5d5d@proxmox.com/
[1]: https://lore.kernel.org/qemu-devel/e13b488e-bf13-44f2-acca-e724d14f43fd@proxmox.com/

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
This commit is contained in:
Fiona Ebner
2024-04-25 17:21:28 +02:00
committed by Thomas Lamprecht
parent 2e71c17f5b
commit f1eed34ac7
73 changed files with 901 additions and 1576 deletions
Download Patch File Download Diff File Expand all files Collapse all files
debian/patches/pve/0017-PVE-add-savevm-async-for-background-state-snapshots.patch
Vendored
+43 -40
View File
@@ -27,7 +27,7 @@ Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
[FE: further improve aborting
adapt to removal of QEMUFileOps
improve condition for entering final stage
adapt to QAPI and other changes for 8.0]
adapt to QAPI and other changes for 8.2]
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
hmp-commands-info.hx | 13 +
@@ -35,13 +35,13 @@ Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
include/migration/snapshot.h | 2 +
include/monitor/hmp.h | 3 +
migration/meson.build | 1 +
migration/savevm-async.c | 531 +++++++++++++++++++++++++++++++++++
migration/savevm-async.c | 534 +++++++++++++++++++++++++++++++++++
monitor/hmp-cmds.c | 38 +++
qapi/migration.json | 34 +++
qapi/misc.json | 16 ++
qemu-options.hx | 12 +
softmmu/vl.c | 10 +
11 files changed, 677 insertions(+)
system/vl.c | 10 +
11 files changed, 680 insertions(+)
create mode 100644 migration/savevm-async.c
diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
@@ -69,10 +69,10 @@ index f5b37eb74a..10fdd822e0 100644
.name = "balloon",
.args_type = "",
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 2cbd0f77a0..e352f86872 100644
index 765349ed14..893c3bd240 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1865,3 +1865,20 @@ SRST
@@ -1875,3 +1875,20 @@ SRST
List event channels in the guest
ERST
#endif
@@ -126,10 +126,10 @@ index 13f9a2dedb..7a7def7530 100644
void coroutine_fn hmp_screendump(Monitor *mon, const QDict *qdict);
void hmp_chardev_add(Monitor *mon, const QDict *qdict);
diff --git a/migration/meson.build b/migration/meson.build
index 37ddcb5d60..07f6057acc 100644
index 0e689eac09..8f9d122187 100644
--- a/migration/meson.build
+++ b/migration/meson.build
@@ -26,6 +26,7 @@ system_ss.add(files(
@@ -27,6 +27,7 @@ system_ss.add(files(
'options.c',
'postcopy-ram.c',
'savevm.c',
@@ -139,10 +139,10 @@ index 37ddcb5d60..07f6057acc 100644
'threadinfo.c',
diff --git a/migration/savevm-async.c b/migration/savevm-async.c
new file mode 100644
index 0000000000..e9fc18fb10
index 0000000000..8f63c4c637
--- /dev/null
+++ b/migration/savevm-async.c
@@ -0,0 +1,531 @@
@@ -0,0 +1,534 @@
+#include "qemu/osdep.h"
+#include "migration/channel-savevm-async.h"
+#include "migration/migration.h"
@@ -441,21 +441,25 @@ index 0000000000..e9fc18fb10
+ * so move there now and after every flush.
+ */
+ aio_co_reschedule_self(qemu_get_aio_context());
+ for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
+ bdrv_graph_co_rdlock();
+ bs = bdrv_first(&it);
+ bdrv_graph_co_rdunlock();
+ while (bs) {
+ /* target has BDRV_O_NO_FLUSH, no sense calling bdrv_flush on it */
+ if (bs == blk_bs(snap_state.target)) {
+ continue;
+ }
+
+ AioContext *bs_ctx = bdrv_get_aio_context(bs);
+ if (bs_ctx != qemu_get_aio_context()) {
+ DPRINTF("savevm: async flushing drive %s\n", bs->filename);
+ aio_co_reschedule_self(bs_ctx);
+ bdrv_graph_co_rdlock();
+ bdrv_flush(bs);
+ bdrv_graph_co_rdunlock();
+ aio_co_reschedule_self(qemu_get_aio_context());
+ if (bs != blk_bs(snap_state.target)) {
+ AioContext *bs_ctx = bdrv_get_aio_context(bs);
+ if (bs_ctx != qemu_get_aio_context()) {
+ DPRINTF("savevm: async flushing drive %s\n", bs->filename);
+ aio_co_reschedule_self(bs_ctx);
+ bdrv_graph_co_rdlock();
+ bdrv_flush(bs);
+ bdrv_graph_co_rdunlock();
+ aio_co_reschedule_self(qemu_get_aio_context());
+ }
+ }
+ bdrv_graph_co_rdlock();
+ bs = bdrv_next(&it);
+ bdrv_graph_co_rdunlock();
+ }
+
+ DPRINTF("timing: async flushing took %ld ms\n",
@@ -535,9 +539,10 @@ index 0000000000..e9fc18fb10
+ * State is cleared in process_savevm_co, but has to be initialized
+ * here (blocking main thread, from QMP) to avoid race conditions.
+ */
+ migrate_init(ms);
+ if (migrate_init(ms, errp)) {
+ return;
+ }
+ memset(&mig_stats, 0, sizeof(mig_stats));
+ memset(&compression_counters, 0, sizeof(compression_counters));
+ ms->to_dst_file = snap_state.file;
+
+ error_setg(&snap_state.blocker, "block device is in use by savevm");
@@ -546,10 +551,8 @@ index 0000000000..e9fc18fb10
+ snap_state.state = SAVE_STATE_ACTIVE;
+ snap_state.finalize_bh = qemu_bh_new(process_savevm_finalize, &snap_state);
+ snap_state.co = qemu_coroutine_create(&process_savevm_co, NULL);
+ qemu_mutex_unlock_iothread();
+ qemu_savevm_state_header(snap_state.file);
+ qemu_savevm_state_setup(snap_state.file);
+ qemu_mutex_lock_iothread();
+
+ /* Async processing from here on out happens in iohandler context, so let
+ * the target bdrv have its home there.
@@ -675,7 +678,7 @@ index 0000000000..e9fc18fb10
+ return ret;
+}
diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index 6c559b48c8..91be698308 100644
index 871898ac46..ef4634e5c1 100644
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -22,6 +22,7 @@
@@ -685,7 +688,7 @@ index 6c559b48c8..91be698308 100644
+#include "qapi/qapi-commands-migration.h"
#include "qapi/qapi-commands-misc.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qerror.h"
#include "qemu/cutils.h"
@@ -443,3 +444,40 @@ void hmp_info_mtree(Monitor *mon, const QDict *qdict)
mtree_info(flatview, dispatch_tree, owner, disabled);
@@ -728,10 +731,10 @@ index 6c559b48c8..91be698308 100644
+ }
+}
diff --git a/qapi/migration.json b/qapi/migration.json
index 8843e74b59..aca0ca1ac1 100644
index 197d3faa43..b41465fbe9 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -291,6 +291,40 @@
@@ -298,6 +298,40 @@
'*dirty-limit-throttle-time-per-round': 'uint64',
'*dirty-limit-ring-full-time': 'uint64'} }
@@ -800,10 +803,10 @@ index cda2effa81..94a58bb0bf 100644
# @CommandLineParameterType:
#
diff --git a/qemu-options.hx b/qemu-options.hx
index 8073f5edf5..dc1ececc9c 100644
index b6b4ad9e67..881b0b3c43 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4483,6 +4483,18 @@ SRST
@@ -4590,6 +4590,18 @@ SRST
Start right away with a saved state (``loadvm`` in monitor)
ERST
@@ -822,11 +825,11 @@ index 8073f5edf5..dc1ececc9c 100644
#ifndef _WIN32
DEF("daemonize", 0, QEMU_OPTION_daemonize, \
"-daemonize daemonize QEMU after initializing\n", QEMU_ARCH_ALL)
diff --git a/softmmu/vl.c b/softmmu/vl.c
index ba6ad8a8df..ddeace306e 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -164,6 +164,7 @@ static const char *accelerators;
diff --git a/system/vl.c b/system/vl.c
index d2a3b3f457..57f7ba0525 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -163,6 +163,7 @@ static const char *accelerators;
static bool have_custom_ram_size;
static const char *ram_memdev_id;
static QDict *machine_opts_dict;
@@ -834,7 +837,7 @@ index ba6ad8a8df..ddeace306e 100644
static QTAILQ_HEAD(, ObjectOption) object_opts = QTAILQ_HEAD_INITIALIZER(object_opts);
static QTAILQ_HEAD(, DeviceOption) device_opts = QTAILQ_HEAD_INITIALIZER(device_opts);
static int display_remote;
@@ -2647,6 +2648,12 @@ void qmp_x_exit_preconfig(Error **errp)
@@ -2715,6 +2716,12 @@ void qmp_x_exit_preconfig(Error **errp)
if (loadvm) {
load_snapshot(loadvm, NULL, false, NULL, &error_fatal);
@@ -847,7 +850,7 @@ index ba6ad8a8df..ddeace306e 100644
}
if (replay_mode != REPLAY_MODE_NONE) {
replay_vmstate_init();
@@ -3196,6 +3203,9 @@ void qemu_init(int argc, char **argv)
@@ -3265,6 +3272,9 @@ void qemu_init(int argc, char **argv)
case QEMU_OPTION_loadvm:
loadvm = optarg;
break;