Support transferring of TAP state (including open fd).
Add new property "local-migration-supported", which defines
whether local-migration is actually supported for this TAP device.
Starting from 11.2 QEMU Machine Types it's enabled by default.
Note, that local-migration (including migrating opened FDs
through migration channel, which must be UNIX socket), is
enabled by global "local" migration parameters. But individual
devices may have additional options to enable/disable it
per device.
The tricky thing, is that we need to know, should we do
call open/connect in TAP initialization code. That means,
that on incoming migration we want to know status of
"local" migration parameter at time of creating TAP device.
So, currently, for incoming local migration only TAP device
created through QMP is supported, as you need to set migration
parameter first (through QMP as well).
So the full picture is:
On source, to start outgoing "local" migration you need:
- migration parameter "local" set to true
- "local-migration-supported" TAP option set to true (the
default, starting from 11.2 QEMU Machine Types)
If at least one of these options is not set, TAP backend
doesn't participate in migration.
On target, things are more difficult:
Same, you need both "local" and "local-migration-supported"
be set. And same, if one of them is not set, TAP backend
is initialized as usual, and doesn't accept any incoming
state.
Additionally, if you are going to set "local", it must be
set before creating the TAP device. If TAP device created
with "local" unset, it initializes as usual. If you enable
"local" after it and start incoming migration, it will fail
in .pre_load handler of TAP backend.
Moreover, there are interface restrictions: if you create TAP
device when QEMU is in INCOMING state, and both "local"
and "local-migration-supported" set, most of TAP options are
not allowed, and script/downscript are required to be explicitly
unset (set to "" or "no").
Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]>
---
In v17 thread we considered making new qapi parameters "unstable".
Still, it was because of doubtful "incoming-fds" parameter. In this
v18 it's completely removed, and we may live only with "local"
migration parameter + "local-migration-supported" TAP option.
This way the series doesn't conflict with suggested by Peter
[PATCH RFC 0/2] migration/vl: new -incoming config:* for early migration
parameters
So, I think, worth making one more iteration as "stable candidate".
If still some doubts, not problem for me to resend with "unstable" features.
hw/core/machine.c | 7 ++
net/tap.c | 162 ++++++++++++++++++++++++++++++++++++++++++++--
qapi/net.json | 23 ++++++-
3 files changed, 185 insertions(+), 7 deletions(-)
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 15886a56b19..2a1abb29041 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -36,10 +36,16 @@
#include "hw/virtio/virtio-pci.h"
#include "hw/virtio/virtio-net.h"
#include "hw/virtio/virtio-iommu.h"
+#include "net/tap.h"
#include "hw/acpi/generic_event_device.h"
#include "qemu/audio.h"
#include "hw/arm/smmuv3.h"
+/*
+ * TODO: When hw_compat_11_1 appears, local-migration-supported=false
+ * for TYPE_TAP_NETDEV should be move to it from hw_compat_11_0.
+ */
+
GlobalProperty hw_compat_11_0[] = {
{ "chardev-vc", "encoding", "cp437" },
{ "tpm-crb", "cap-chunk", "off" },
@@ -49,6 +55,7 @@ GlobalProperty hw_compat_11_0[] = {
{ TYPE_ARM_SMMUV3, "ssidsize", "0" },
{ TYPE_ARM_SMMUV3, "oas", "44" },
{ "migration", "switchover-ack-legacy", "on" },
+ { TYPE_TAP_NETDEV, "local-migration-supported", "false" },
@@ -1005,6 +1123,23 @@ int net_init_tap(const Netdev *netdev, const char *name,
return -1;
}
+ incoming_fds = tap->local_migration_supported && migrate_local() &&
+ runstate_check(RUN_STATE_INMIGRATE);
+
+ if (incoming_fds &&
+ (tap->fd || tap->fds || tap->helper || tap->br || tap->ifname ||
+ tap->has_sndbuf || tap->has_vnet_hdr ||
+ !tap_is_explicit_no_script(tap->script) ||
+ !tap_is_explicit_no_script(tap->downscript))) {
+ error_setg(errp, "Local incoming migration of TAP device (-incoming, "
+ "migration parameter @local is set, "
+ "TAP parameter @local-migration-supported is set) "
+ "is incompatible with "
+ "fd=, fds=, helper=, br=, ifname=, sndbuf= and vnet_hdr=, "
+ "and requires explicit empty script= and downscript=");
+ return -1;
+ }
