[libvirt] [PATCH 2/6] Added public API to enable post-copy migration

[Jiri Denemark]

On Tue, Sep 23, 2014 at 16:09:57 +0200, Cristian Klein wrote:
> Added a new `libvirt` migration flag `VIR_MIGRATE_POSTCOPY` and the
> necessary code to pass this flag to qemu as migration capability.
> 
> Signed-off-by: Cristian Klein <cristian.klein at cs.umu.se>
> ---
>  include/libvirt/libvirt.h.in |  1 +
>  src/libvirt.c                |  7 +++++++
>  src/qemu/qemu_migration.c    | 43 +++++++++++++++++++++++++++++++++++++++++++
>  src/qemu/qemu_migration.h    |  3 ++-
>  4 files changed, 53 insertions(+), 1 deletion(-)
> 
> diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
> index 6371b7b..bdc33c6 100644
> --- a/include/libvirt/libvirt.h.in
> +++ b/include/libvirt/libvirt.h.in
> @@ -1225,6 +1225,7 @@ typedef enum {
>      VIR_MIGRATE_ABORT_ON_ERROR    = (1 << 12), /* abort migration on I/O errors happened during migration */
>      VIR_MIGRATE_AUTO_CONVERGE     = (1 << 13), /* force convergence */
>      VIR_MIGRATE_RDMA_PIN_ALL      = (1 << 14), /* RDMA memory pinning */
> +    VIR_MIGRATE_POSTCOPY          = (1 << 15), /* enable (but don't start) post-copy */
>  } virDomainMigrateFlags;
>  
>  
> diff --git a/src/libvirt.c b/src/libvirt.c
> index 1a285ca..33aeafa 100644
> --- a/src/libvirt.c
> +++ b/src/libvirt.c
> @@ -5265,6 +5265,7 @@ virDomainMigrateDirect(virDomainPtr domain,
>   *                                 automatically when supported).
>   *   VIR_MIGRATE_UNSAFE    Force migration even if it is considered unsafe.
>   *   VIR_MIGRATE_OFFLINE Migrate offline
> + *   VIR_MIGRATE_POSTCOPY Enable (but don't start) post-copy
>   *
>   * VIR_MIGRATE_TUNNELLED requires that VIR_MIGRATE_PEER2PEER be set.
>   * Applications using the VIR_MIGRATE_PEER2PEER flag will probably
> @@ -5291,6 +5292,12 @@ virDomainMigrateDirect(virDomainPtr domain,
>   * can use either VIR_MIGRATE_NON_SHARED_DISK or
>   * VIR_MIGRATE_NON_SHARED_INC as they are mutually exclusive.
>   *
> + * If you want to enable post-copy migration you must set the
> + * VIR_MIGRATE_POSTCOPY flag. Once migration is active, you may
> + * start post-copy by calling virDomainMigrateStartPostCopy.
> + * When to start post-copy is entirely left to the user, libvirt
> + * only implements the necessary mechanism.
> + *
>   * In either case it is typically only necessary to specify a
>   * URI if the destination host has multiple interfaces and a
>   * specific interface is required to transmit migration data.
> diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
> index a5bd825..bd1f2d6 100644
> --- a/src/qemu/qemu_migration.c
> +++ b/src/qemu/qemu_migration.c
> @@ -1799,6 +1799,45 @@ qemuMigrationSetOffline(virQEMUDriverPtr driver,
>  
>  
>  static int
> +qemuMigrationSetPostCopy(virQEMUDriverPtr driver,
> +                            virDomainObjPtr vm,
> +                            qemuDomainAsyncJob job)

s/   // in the two lines above to fix indentation.

> +{
> +    qemuDomainObjPrivatePtr priv = vm->privateData;
> +    int ret;
> +
> +    if (qemuDomainObjEnterMonitorAsync(driver, vm, job) < 0)
> +        return -1;
> +
> +    ret = qemuMonitorGetMigrationCapability(
> +                priv->mon,
> +                QEMU_MONITOR_MIGRATION_CAPS_POSTCOPY);

QEMU_MONITOR_MIGRATION_CAPS_POSTCOPY is not defined anywhere in this
patchset. It seems you forgot to update qemu_monitor.[ch].

> +
> +    if (ret < 0) {
> +        goto cleanup;
> +    } else if (ret == 0) {
> +        if (job == QEMU_ASYNC_JOB_MIGRATION_IN) {
> +            virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
> +                           _("Post-copy migration is not supported by "
> +                             "target QEMU binary"));
> +        } else {
> +            virReportError(VIR_ERR_ARGUMENT_UNSUPPORTED, "%s",
> +                           _("Post-copy migration is not supported by "
> +                             "source QEMU binary"));
> +        }
> +        ret = -1;
> +        goto cleanup;
> +    }
> +
> +    ret = qemuMonitorSetMigrationCapability(
> +                priv->mon,
> +                QEMU_MONITOR_MIGRATION_CAPS_POSTCOPY);
> +
> + cleanup:
> +    qemuDomainObjExitMonitor(driver, vm);
> +    return ret;
> +}
> +static int
>  qemuMigrationSetCompression(virQEMUDriverPtr driver,
>                              virDomainObjPtr vm,
>                              qemuDomainAsyncJob job)
> @@ -3580,6 +3619,10 @@ qemuMigrationRun(virQEMUDriverPtr driver,
>      if (flags & VIR_MIGRATE_RDMA_PIN_ALL &&
>          qemuMigrationSetPinAll(driver, vm,
>                                 QEMU_ASYNC_JOB_MIGRATION_OUT) < 0)
> +
> +    if (flags & VIR_MIGRATE_POSTCOPY &&
> +        qemuMigrationSetPostCopy(driver, vm,
> +                                 QEMU_ASYNC_JOB_MIGRATION_OUT) < 0)
>          goto cleanup;
>  
>      if (qemuDomainObjEnterMonitorAsync(driver, vm,

I'd expect similar thing would need to be done in the Prepare phase on
destination... However, if destination does not need to set the
capability, we at least need to check if destination QEMU supports it
and report failure from Prepare if it doesn't. And the
QEMU_ASYNC_JOB_MIGRATION_IN branch in qemuMigrationSetPostCopy would be
unreachable in that case.

> diff --git a/src/qemu/qemu_migration.h b/src/qemu/qemu_migration.h
> index e7a90c3..349c9c4 100644
> --- a/src/qemu/qemu_migration.h
> +++ b/src/qemu/qemu_migration.h
> @@ -41,7 +41,8 @@
>       VIR_MIGRATE_COMPRESSED |                   \
>       VIR_MIGRATE_ABORT_ON_ERROR |               \
>       VIR_MIGRATE_AUTO_CONVERGE |                \
> -     VIR_MIGRATE_RDMA_PIN_ALL)
> +     VIR_MIGRATE_RDMA_PIN_ALL |                 \
> +     VIR_MIGRATE_POSTCOPY)
>  
>  /* All supported migration parameters and their types. */
>  # define QEMU_MIGRATION_PARAMETERS                              \

Jirka