Add the cpr-transfer migration mode. Usage:
qemu-system-$arch -machine anon-alloc=memfd ...
start new QEMU with "-incoming <uri-1> -cpr-uri <uri-2>"
Issue commands to old QEMU:
migrate_set_parameter mode cpr-transfer
migrate_set_parameter cpr-uri <uri-2>
migrate -d <uri-1>
The migrate command stops the VM, saves CPR state to uri-2, saves
normal migration state to uri-1, and old QEMU enters the postmigrate
state. The user starts new QEMU on the same host as old QEMU, with the
same arguments as old QEMU, plus the -incoming option. Guest RAM is
preserved in place, albeit with new virtual addresses in new QEMU.
This mode requires a second migration channel, specified by the
cpr-uri migration property on the outgoing side, and by the cpr-uri
QEMU command-line option on the incoming side. The channel must
be a type, such as unix socket, that supports SCM_RIGHTS.
Memory-backend objects must have the share=on attribute, but
memory-backend-epc is not supported. The VM must be started with
the '-machine anon-alloc=memfd' option, which allows anonymous
memory to be transferred in place to the new process. The memfds
are kept open by sending the descriptors to new QEMU via the
cpr-uri, which must support SCM_RIGHTS, and they are mmap'd
in new QEMU.
Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
---
include/migration/cpr.h | 1 +
migration/cpr.c | 34 +++++++++++++++++++----
migration/migration.c | 69 +++++++++++++++++++++++++++++++++++++++++++++--
migration/migration.h | 2 ++
migration/ram.c | 2 ++
migration/vmstate-types.c | 5 ++--
qapi/migration.json | 27 ++++++++++++++++++-
stubs/vmstate.c | 7 +++++
8 files changed, 137 insertions(+), 10 deletions(-)
diff --git a/include/migration/cpr.h b/include/migration/cpr.h
index e886c98..5cd373f 100644
--- a/include/migration/cpr.h
+++ b/include/migration/cpr.h
@@ -30,6 +30,7 @@ int cpr_state_save(Error **errp);
int cpr_state_load(Error **errp);
void cpr_state_close(void);
struct QIOChannel *cpr_state_ioc(void);
+bool cpr_needed_for_reuse(void *opaque);
QEMUFile *cpr_transfer_output(const char *uri, Error **errp);
QEMUFile *cpr_transfer_input(const char *uri, Error **errp);
diff --git a/migration/cpr.c b/migration/cpr.c
index 86f66c1..911b556 100644
--- a/migration/cpr.c
+++ b/migration/cpr.c
@@ -9,6 +9,7 @@
#include "qapi/error.h"
#include "migration/cpr.h"
#include "migration/misc.h"
+#include "migration/options.h"
#include "migration/qemu-file.h"
#include "migration/savevm.h"
#include "migration/vmstate.h"
@@ -57,7 +58,7 @@ static const VMStateDescription vmstate_cpr_fd = {
VMSTATE_UINT32(namelen, CprFd),
VMSTATE_VBUFFER_ALLOC_UINT32(name, CprFd, 0, NULL, namelen),
VMSTATE_INT32(id, CprFd),
- VMSTATE_INT32(fd, CprFd),
+ VMSTATE_FD(fd, CprFd),
VMSTATE_END_OF_LIST()
}
};
@@ -174,9 +175,16 @@ int cpr_state_save(Error **errp)
{
int ret;
QEMUFile *f;
+ MigMode mode = migrate_mode();
- /* set f based on mode in a later patch in this series */
- return 0;
+ if (mode == MIG_MODE_CPR_TRANSFER) {
+ f = cpr_transfer_output(migrate_cpr_uri(), errp);
+ } else {
+ return 0;
+ }
+ if (!f) {
+ return -1;
+ }
qemu_put_be32(f, QEMU_CPR_FILE_MAGIC);
qemu_put_be32(f, QEMU_CPR_FILE_VERSION);
@@ -205,8 +213,18 @@ int cpr_state_load(Error **errp)
uint32_t v;
QEMUFile *f;
- /* set f based on mode in a later patch in this series */
- return 0;
+ /*
+ * Mode will be loaded in CPR state, so cannot use it to decide which
+ * form of state to load.
+ */
+ if (cpr_uri) {
+ f = cpr_transfer_input(cpr_uri, errp);
+ } else {
+ return 0;
+ }
+ if (!f) {
+ return -1;
+ }
v = qemu_get_be32(f);
if (v != QEMU_CPR_FILE_MAGIC) {
@@ -243,3 +261,9 @@ void cpr_state_close(void)
cpr_state_file = NULL;
}
}
+
+bool cpr_needed_for_reuse(void *opaque)
+{
+ MigMode mode = migrate_mode();
+ return mode == MIG_MODE_CPR_TRANSFER;
+}
diff --git a/migration/migration.c b/migration/migration.c
index 3301583..73b85aa 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -76,6 +76,7 @@
static NotifierWithReturnList migration_state_notifiers[] = {
NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_NORMAL),
NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_CPR_REBOOT),
+ NOTIFIER_ELEM_INIT(migration_state_notifiers, MIG_MODE_CPR_TRANSFER),
};
/* Messages sent on the return path from destination to source */
@@ -109,6 +110,7 @@ static int migration_maybe_pause(MigrationState *s,
static void migrate_fd_cancel(MigrationState *s);
static bool close_return_path_on_source(MigrationState *s);
static void migration_completion_end(MigrationState *s);
+static void migrate_hup_delete(MigrationState *s);
static void migration_downtime_start(MigrationState *s)
{
@@ -204,6 +206,12 @@
migration_channels_and_transport_compatible(MigrationAddress *addr,
return false;
}
+ if (migrate_mode() == MIG_MODE_CPR_TRANSFER &&
+ addr->transport == MIGRATION_ADDRESS_TYPE_FILE) {
+ error_setg(errp, "Migration requires streamable transport (eg unix)");
+ return false;
+ }
+
return true;
}
@@ -316,6 +324,7 @@ void migration_cancel(const Error *error)
qmp_cancel_vcpu_dirty_limit(false, -1, NULL);
}
migrate_fd_cancel(current_migration);
+ migrate_hup_delete(current_migration);
}
void migration_shutdown(void)
@@ -718,6 +727,9 @@ static void qemu_start_incoming_migration(const char *uri,
bool has_channels,
} else {
error_setg(errp, "unknown migration protocol: %s", uri);
}
+
+ /* Close cpr socket to tell source that we are listening */
+ cpr_state_close();
}
static void process_incoming_migration_bh(void *opaque)
@@ -1414,6 +1426,8 @@ static void migrate_fd_cleanup(MigrationState *s)
s->vmdesc = NULL;
qemu_savevm_state_cleanup();
+ cpr_state_close();
+ migrate_hup_delete(s);
close_return_path_on_source(s);
@@ -1698,7 +1712,9 @@ bool migration_thread_is_self(void)
bool migrate_mode_is_cpr(MigrationState *s)
{
- return s->parameters.mode == MIG_MODE_CPR_REBOOT;
+ MigMode mode = s->parameters.mode;
+ return mode == MIG_MODE_CPR_REBOOT ||
+ mode == MIG_MODE_CPR_TRANSFER;
}
int migrate_init(MigrationState *s, Error **errp)
@@ -2033,6 +2049,12 @@ static bool migrate_prepare(MigrationState *s, bool
resume, Error **errp)
return false;
}
+ if (migrate_mode() == MIG_MODE_CPR_TRANSFER &&
+ !s->parameters.cpr_uri) {
+ error_setg(errp, "cpr-transfer mode requires setting cpr-uri");
+ return false;
+ }
+
if (migration_is_blocked(errp)) {
return false;
}
@@ -2076,6 +2098,37 @@ static bool migrate_prepare(MigrationState *s, bool
resume, Error **errp)
static void qmp_migrate_finish(MigrationAddress *addr, bool resume_requested,
Error **errp);
+static void migrate_hup_add(MigrationState *s, QIOChannel *ioc, GSourceFunc cb,
+ void *opaque)
+{
+ s->hup_source = qio_channel_create_watch(ioc, G_IO_HUP);
+ g_source_set_callback(s->hup_source, cb, opaque, NULL);
+ g_source_attach(s->hup_source, NULL);
+}
+
+static void migrate_hup_delete(MigrationState *s)
+{
+ if (s->hup_source) {
+ g_source_destroy(s->hup_source);
+ g_source_unref(s->hup_source);
+ s->hup_source = NULL;
+ }
+}
+
+static gboolean qmp_migrate_finish_cb(QIOChannel *channel,
+ GIOCondition cond,
+ void *opaque)
+{
+ MigrationAddress *addr = opaque;
+
+ qmp_migrate_finish(addr, false, NULL);
+
+ cpr_state_close();
+ migrate_hup_delete(migrate_get_current());
+ qapi_free_MigrationAddress(addr);
+ return G_SOURCE_REMOVE;
+}
+
void qmp_migrate(const char *uri, bool has_channels,
MigrationChannelList *channels, bool has_detach, bool detach,
bool has_resume, bool resume, Error **errp)
@@ -2136,7 +2189,19 @@ void qmp_migrate(const char *uri, bool has_channels,
goto out;
}
- qmp_migrate_finish(addr, resume_requested, errp);
+ /*
+ * For cpr-transfer, the target may not be listening yet on the migration
+ * channel, because first it must finish cpr_load_state. The target tells
+ * us it is listening by closing the cpr-state socket. Wait for that HUP
+ * event before connecting in qmp_migrate_finish.
+ */
+ if (s->parameters.mode == MIG_MODE_CPR_TRANSFER) {
+ migrate_hup_add(s, cpr_state_ioc(), (GSourceFunc)qmp_migrate_finish_cb,
+ QAPI_CLONE(MigrationAddress, addr));
+
+ } else {
+ qmp_migrate_finish(addr, resume_requested, errp);
+ }
out:
if (local_err) {
diff --git a/migration/migration.h b/migration/migration.h
index 38aa140..74c167b 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -457,6 +457,8 @@ struct MigrationState {
bool switchover_acked;
/* Is this a rdma migration */
bool rdma_migration;
+
+ GSource *hup_source;
};
void migrate_set_state(MigrationStatus *state, MigrationStatus old_state,
diff --git a/migration/ram.c b/migration/ram.c
index 81eda27..e2cef50 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -216,7 +216,9 @@ static bool postcopy_preempt_active(void)
bool migrate_ram_is_ignored(RAMBlock *block)
{
+ MigMode mode = migrate_mode();
return !qemu_ram_is_migratable(block) ||
+ mode == MIG_MODE_CPR_TRANSFER ||
(migrate_ignore_shared() && qemu_ram_is_shared(block)
&& qemu_ram_is_named_file(block));
}
diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
index 6e45a4a..b5a55b8 100644
--- a/migration/vmstate-types.c
+++ b/migration/vmstate-types.c
@@ -15,6 +15,7 @@
#include "qemu-file.h"
#include "migration.h"
#include "migration/vmstate.h"
+#include "migration/client-options.h"
#include "qemu/error-report.h"
#include "qemu/queue.h"
#include "trace.h"
@@ -321,7 +322,7 @@ static int get_fd(QEMUFile *f, void *pv, size_t size,
{
int32_t *v = pv;
qemu_get_sbe32s(f, v);
- if (*v < 0) {
+ if (*v < 0 || migrate_mode() != MIG_MODE_CPR_TRANSFER) {
return 0;
}
*v = qemu_file_get_fd(f);
@@ -334,7 +335,7 @@ static int put_fd(QEMUFile *f, void *pv, size_t size,
int32_t *v = pv;
qemu_put_sbe32s(f, v);
- if (*v < 0) {
+ if (*v < 0 || migrate_mode() != MIG_MODE_CPR_TRANSFER) {
return 0;
}
return qemu_file_put_fd(f, *v);
diff --git a/qapi/migration.json b/qapi/migration.json
index c0d8bcc..f51b4cb 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -611,9 +611,34 @@
# or COLO.
#
# (since 8.2)
+#
+# @cpr-transfer: This mode allows the user to transfer a guest to a
+# new QEMU instance on the same host with minimal guest pause
+# time, by preserving guest RAM in place, albeit with new virtual
+# addresses in new QEMU.
+#
+# The user starts new QEMU on the same host as old QEMU, with the
+# the same arguments as old QEMU, plus the -incoming option. The
+# user issues the migrate command to old QEMU, which stops the VM,
+# saves state to the migration channels, and enters the
+# postmigrate state. Execution resumes in new QEMU. Guest RAM is
+# preserved in place, albeit with new virtual addresses in new
+# QEMU. The incoming migration channel cannot be a file type.
+#
+# This mode requires a second migration channel, specified by the
+# cpr-uri migration property on the outgoing side, and by
+# the cpr-uri QEMU command-line option on the incoming
+# side. The channel must be a type, such as unix socket, that
+# supports SCM_RIGHTS.
+#
+# Memory-backend objects must have the share=on attribute, but
+# memory-backend-epc is not supported. The VM must be started
+# with the '-machine anon-alloc=memfd' option.
+#
+# (since 9.2)
##
{ 'enum': 'MigMode',
- 'data': [ 'normal', 'cpr-reboot' ] }
+ 'data': [ 'normal', 'cpr-reboot', 'cpr-transfer' ] }
##
# @ZeroPageDetection:
diff --git a/stubs/vmstate.c b/stubs/vmstate.c
index 8513d92..c190762 100644
--- a/stubs/vmstate.c
+++ b/stubs/vmstate.c
@@ -1,5 +1,7 @@
#include "qemu/osdep.h"
#include "migration/vmstate.h"
+#include "qapi/qapi-types-migration.h"
+#include "migration/client-options.h"
int vmstate_register_with_alias_id(VMStateIf *obj,
uint32_t instance_id,
@@ -21,3 +23,8 @@ bool vmstate_check_only_migratable(const VMStateDescription
*vmsd)
{
return true;
}
+
+MigMode migrate_mode(void)
+{
+ return MIG_MODE_NORMAL;
+}
--
1.8.3.1
