[libvirt] [PATCH 2/5] qemu: Store supported migration capabilities in a bitmap

[John Ferlan]

On 10/18/2017 07:29 AM, Jiri Denemark wrote:
> Each time we need to check whether a given migration capability is
> supported by QEMU, we call query-migrate-capabilities QMP command and
> lookup the capability in the returned list. Asking for the list of
> supported capabilities once when we connect to QEMU and storing the
> result in a bitmap is much better and we don't need to enter a monitor
> just to check whether a migration capability is supported.
> 
> Signed-off-by: Jiri Denemark <jdenemar at redhat.com>
> ---
>  src/qemu/qemu_domain.c  | 68 +++++++++++++++++++++++++++++++++++++++++++++++++
>  src/qemu/qemu_domain.h  |  9 +++++++
>  src/qemu/qemu_process.c | 13 +---------
>  3 files changed, 78 insertions(+), 12 deletions(-)
> 

There's no corresponding adjustment to qemuDomainObjPrivateXMLFormat and
qemuDomainObjPrivateXMLParse in order to handle the restart scenario.

The rest of this looks OK, but do you need the Format/Parse logic for
the bitmap?  It was late in my day and I was too lazy to go chase seeing
as I already did the merging ;-)

John

> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index 05e8b96aa4..a8cabc5727 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -1767,6 +1767,9 @@ qemuDomainObjPrivateDataClear(qemuDomainObjPrivatePtr priv)
>      priv->namespaces = NULL;
>  
>      priv->reconnectBlockjobs = VIR_TRISTATE_BOOL_ABSENT;
> +
> +    virBitmapFree(priv->migrationCaps);
> +    priv->migrationCaps = NULL;
>  }
>  
>  
> @@ -10122,3 +10125,68 @@ qemuDomainGetMachineName(virDomainObjPtr vm)
>  
>      return ret;
>  }
> +
> +
> +int
> +qemuDomainCheckMigrationCapabilities(virQEMUDriverPtr driver,
> +                                     virDomainObjPtr vm,
> +                                     qemuDomainAsyncJob asyncJob)
> +{
> +    qemuDomainObjPrivatePtr priv = vm->privateData;
> +    char **caps = NULL;
> +    char **capStr;
> +    int ret = -1;
> +    int rc;
> +
> +    if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) < 0)
> +        return -1;
> +
> +    rc = qemuMonitorGetMigrationCapabilities(priv->mon, &caps);
> +
> +    if (qemuDomainObjExitMonitor(driver, vm) < 0 || rc < 0)
> +        goto cleanup;
> +
> +    if (!caps) {
> +        ret = 0;
> +        goto cleanup;
> +    }
> +
> +    priv->migrationCaps = virBitmapNew(QEMU_MONITOR_MIGRATION_CAPS_LAST);
> +    if (!priv->migrationCaps)
> +        goto cleanup;
> +
> +    for (capStr = caps; *capStr; capStr++) {
> +        int cap = qemuMonitorMigrationCapsTypeFromString(*capStr);
> +
> +        if (cap < 0) {
> +            VIR_DEBUG("Unknown migration capability: '%s'", *capStr);
> +        } else {
> +            ignore_value(virBitmapSetBit(priv->migrationCaps, cap));
> +            VIR_DEBUG("Found migration capability: '%s'", *capStr);
> +        }
> +    }
> +
> +    if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATION_EVENT)) {
> +        if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) < 0)
> +            goto cleanup;
> +
> +        rc = qemuMonitorSetMigrationCapability(priv->mon,
> +                                               QEMU_MONITOR_MIGRATION_CAPS_EVENTS,
> +                                               true);
> +
> +        if (qemuDomainObjExitMonitor(driver, vm) < 0)
> +            goto cleanup;
> +
> +        if (rc < 0) {
> +            virResetLastError();
> +            VIR_DEBUG("Cannot enable migration events; clearing capability");
> +            virQEMUCapsClear(priv->qemuCaps, QEMU_CAPS_MIGRATION_EVENT);
> +        }
> +    }
> +
> +    ret = 0;
> +
> + cleanup:
> +    virStringListFree(caps);
> +    return ret;
> +}
> diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
> index 5201c6a0ac..fb20d8ea63 100644
> --- a/src/qemu/qemu_domain.h
> +++ b/src/qemu/qemu_domain.h
> @@ -323,6 +323,10 @@ struct _qemuDomainObjPrivate {
>  
>      /* Tracks blockjob state for vm. Valid only while reconnecting to qemu. */
>      virTristateBool reconnectBlockjobs;
> +
> +    /* Migration capabilities. Rechecked on reconnect, not to be saved in
> +     * private XML. */
> +    virBitmapPtr migrationCaps;
>  };
>  
>  # define QEMU_DOMAIN_PRIVATE(vm)	\
> @@ -978,4 +982,9 @@ qemuDomainFixupCPUs(virDomainObjPtr vm,
>  char *
>  qemuDomainGetMachineName(virDomainObjPtr vm);
>  
> +int
> +qemuDomainCheckMigrationCapabilities(virQEMUDriverPtr driver,
> +                                     virDomainObjPtr vm,
> +                                     qemuDomainAsyncJob asyncJob);
> +
>  #endif /* __QEMU_DOMAIN_H__ */
> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> index 24675498a2..cea2f90ce1 100644
> --- a/src/qemu/qemu_process.c
> +++ b/src/qemu/qemu_process.c
> @@ -1816,18 +1816,7 @@ qemuConnectMonitor(virQEMUDriverPtr driver, virDomainObjPtr vm, int asyncJob,
>      if (qemuProcessInitMonitor(driver, vm, asyncJob) < 0)
>          return -1;
>  
> -    if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) < 0)
> -        return -1;
> -
> -    if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_MIGRATION_EVENT) &&
> -        qemuMonitorSetMigrationCapability(priv->mon,
> -                                          QEMU_MONITOR_MIGRATION_CAPS_EVENTS,
> -                                          true) < 0) {
> -        VIR_DEBUG("Cannot enable migration events; clearing capability");
> -        virQEMUCapsClear(priv->qemuCaps, QEMU_CAPS_MIGRATION_EVENT);
> -    }
> -
> -    if (qemuDomainObjExitMonitor(driver, vm) < 0)
> +    if (qemuDomainCheckMigrationCapabilities(driver, vm, asyncJob) < 0)
>          return -1;
>  
>      return 0;
>