Re: [PATCH v3 3/4] migration/qapi: Replace @MigrateSetParameters with @MigrationParameters

[Markus Armbruster]

Peter Xu <peterx@redhat.com> writes:

> Quotting from Markus in his replies:

Quoting

Suggest something like "Markus recently wrote:"

>   migrate-set-parameters sets migration parameters, and
>   query-migrate-parameters gets them.  Unsurprisingly, the former's
>   argument type MigrateSetParameters is quite close to the latter's
>   return type MigrationParameters.  The differences are subtle:
>
>   1. Since migrate-set-parameters supports setting selected parameters,
>      its arguments must all be optional (so you can omit the ones you
>      don't want to change).  query-migrate-parameters results are also
>      all optional, but almost all of them are in fact always present.
>
>   2. For parameters @tls_creds, @tls_hostname, @tls_authz,
>      migrate-set-parameters interprets special value "" as "reset to
>      default".  Works, because "" is semantically invalid.  Not a
>      general solution, because a semantically invalid value need not
>      exist.  Markus added a general solution in commit 01fa559826
>      ("migration: Use JSON null instead of "" to reset parameter to
>      default").  This involved changing the type from 'str' to
>      'StrOrNull'.
>
>   3. When parameter @block-bitmap-mapping has not been set,
>      query-migrate-parameters does not return it (absent optional
>      member).  Clean (but undocumented).  When parameters @tls_creds,
>      @tls_hostname, @tls_authz have not been set, it returns the
>      semantically invalid value "".  Not so clean (and just as
>      undocumented).
>
> Here to deduplicate the two objects: keep @MigrationParameters as the name
> of object to use in both places, drop @MigrateSetParameters, at the
> meantime switch types of @tls* fields from "str" to "StrOrNull" types.

Suggest

  Eliminate the duplication follows.

  Change MigrationParameters members @tls_creds, @tls_hostname,
  @tls_authz to StrOrNull.  query-migrate-parameters will of course
  never return null.

  Since these members are qdev properties, we need property machinery
  for StrOrNull: DEFINE_PROP_STR_OR_NULL().

  Switch migrate-set-parameters to MigrationParameters, and delete
  MigrateSetParameters.

Can you make this patch do just this de-duplication, and everything else
(described below) separately?

> I found that the TLS code wasn't so much relying on tls_* fields being
> non-NULL at all.  Actually on the other way round: if we set tls_authz to
> an empty string (NOTE: currently, migrate_init() missed initializing
> tls_authz; also touched it up in this patch), we can already fail one of
> the migration-test (tls/x509/default-host), as qauthz_is_allowed_by_id()
> will assume tls_authz set even if tls_auths is an empty string.
>
> It means we're actually relying on tls_* fields being NULL even if it's the
> empty string.
>
> Let's just make it a rule to return NULL for empty string on these fields
> internally.  For that, when converting a StrOrNull into a char* (where we
> introduced a helper here in this patch) we'll also make the empty string to
> be NULL, to make it always work.  And it doesn't show any issue either when
> applying that logic to both tls_creds and tls_hostname.
>
> With above, we can safely change both migration_tls_client_create() and
> migrate_tls() to not check the empty string too finally.. not needed
> anymore.
>
> Also, we can drop the hackish conversions in qmp_migrate_set_parameters()
> where we want to make sure it's a QSTRING; it's not needed now.
>
> This greatly deduplicates the code not only in qapi/migration.json, but
> also in the generic migration code.
>
> Markus helped greatly with this patch.  Besides a better commit
> message (where I just "stole" from the reply), debugged and resolved a
> double free, but also provided the StrOrNull property implementation to be
> used in MigrationState object when switching tls_* fields to StrOrNull.
>
> Co-developed-by: Markus Armbruster <armbru@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  qapi/migration.json            | 191 +---------------------------
>  include/hw/qdev-properties.h   |   3 +
>  migration/options.h            |   3 +
>  hw/core/qdev-properties.c      |  40 ++++++
>  migration/migration-hmp-cmds.c |  20 +--
>  migration/options.c            | 220 ++++++++++-----------------------
>  migration/tls.c                |   3 +-
>  7 files changed, 125 insertions(+), 355 deletions(-)
>
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 8843e74b59..45d69787ae 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -851,189 +851,6 @@
>             { 'name': 'x-vcpu-dirty-limit-period', 'features': ['unstable'] },
>             'vcpu-dirty-limit'] }
>  
> -##
> -# @MigrateSetParameters:
> -#
> -# @announce-initial: Initial delay (in milliseconds) before sending
> -#     the first announce (Since 4.0)
> -#
> -# @announce-max: Maximum delay (in milliseconds) between packets in
> -#     the announcement (Since 4.0)
> -#
> -# @announce-rounds: Number of self-announce packets sent after
> -#     migration (Since 4.0)
> -#
> -# @announce-step: Increase in delay (in milliseconds) between
> -#     subsequent packets in the announcement (Since 4.0)
> -#
> -# @compress-level: compression level
> -#
> -# @compress-threads: compression thread count
> -#
> -# @compress-wait-thread: Controls behavior when all compression
> -#     threads are currently busy.  If true (default), wait for a free
> -#     compression thread to become available; otherwise, send the page
> -#     uncompressed.  (Since 3.1)
> -#
> -# @decompress-threads: decompression thread count
> -#
> -# @throttle-trigger-threshold: The ratio of bytes_dirty_period and
> -#     bytes_xfer_period to trigger throttling.  It is expressed as
> -#     percentage.  The default value is 50. (Since 5.0)
> -#
> -# @cpu-throttle-initial: Initial percentage of time guest cpus are
> -#     throttled when migration auto-converge is activated.  The
> -#     default value is 20. (Since 2.7)
> -#
> -# @cpu-throttle-increment: throttle percentage increase each time
> -#     auto-converge detects that migration is not making progress.
> -#     The default value is 10. (Since 2.7)
> -#
> -# @cpu-throttle-tailslow: Make CPU throttling slower at tail stage At
> -#     the tail stage of throttling, the Guest is very sensitive to CPU
> -#     percentage while the @cpu-throttle -increment is excessive
> -#     usually at tail stage.  If this parameter is true, we will
> -#     compute the ideal CPU percentage used by the Guest, which may
> -#     exactly make the dirty rate match the dirty rate threshold.
> -#     Then we will choose a smaller throttle increment between the one
> -#     specified by @cpu-throttle-increment and the one generated by
> -#     ideal CPU percentage.  Therefore, it is compatible to
> -#     traditional throttling, meanwhile the throttle increment won't
> -#     be excessive at tail stage.  The default value is false.  (Since
> -#     5.1)
> -#
> -# @tls-creds: ID of the 'tls-creds' object that provides credentials
> -#     for establishing a TLS connection over the migration data
> -#     channel.  On the outgoing side of the migration, the credentials
> -#     must be for a 'client' endpoint, while for the incoming side the
> -#     credentials must be for a 'server' endpoint.  Setting this to a
> -#     non-empty string enables TLS for all migrations.  An empty
> -#     string means that QEMU will use plain text mode for migration,
> -#     rather than TLS (Since 2.9) Previously (since 2.7), this was
> -#     reported by omitting tls-creds instead.
> -#
> -# @tls-hostname: hostname of the target host for the migration.  This
> -#     is required when using x509 based TLS credentials and the
> -#     migration URI does not already include a hostname.  For example
> -#     if using fd: or exec: based migration, the hostname must be
> -#     provided so that the server's x509 certificate identity can be
> -#     validated.  (Since 2.7) An empty string means that QEMU will use
> -#     the hostname associated with the migration URI, if any.  (Since
> -#     2.9) Previously (since 2.7), this was reported by omitting
> -#     tls-hostname instead.
> -#
> -# @max-bandwidth: to set maximum speed for migration.  maximum speed
> -#     in bytes per second.  (Since 2.8)
> -#
> -# @downtime-limit: set maximum tolerated downtime for migration.
> -#     maximum downtime in milliseconds (Since 2.8)
> -#
> -# @x-checkpoint-delay: the delay time between two COLO checkpoints.
> -#     (Since 2.8)
> -#
> -# @block-incremental: Affects how much storage is migrated when the
> -#     block migration capability is enabled.  When false, the entire
> -#     storage backing chain is migrated into a flattened image at the
> -#     destination; when true, only the active qcow2 layer is migrated
> -#     and the destination must already have access to the same backing
> -#     chain as was used on the source.  (since 2.10)
> -#
> -# @multifd-channels: Number of channels used to migrate data in
> -#     parallel.  This is the same number that the number of sockets
> -#     used for migration.  The default value is 2 (since 4.0)
> -#
> -# @xbzrle-cache-size: cache size to be used by XBZRLE migration.  It
> -#     needs to be a multiple of the target page size and a power of 2
> -#     (Since 2.11)
> -#
> -# @max-postcopy-bandwidth: Background transfer bandwidth during
> -#     postcopy.  Defaults to 0 (unlimited).  In bytes per second.
> -#     (Since 3.0)
> -#
> -# @max-cpu-throttle: maximum cpu throttle percentage.  The default
> -#     value is 99. (Since 3.1)
> -#
> -# @multifd-compression: Which compression method to use.  Defaults to
> -#     none.  (Since 5.0)
> -#
> -# @multifd-zlib-level: Set the compression level to be used in live
> -#     migration, the compression level is an integer between 0 and 9,
> -#     where 0 means no compression, 1 means the best compression
> -#     speed, and 9 means best compression ratio which will consume
> -#     more CPU. Defaults to 1. (Since 5.0)
> -#
> -# @multifd-zstd-level: Set the compression level to be used in live
> -#     migration, the compression level is an integer between 0 and 20,
> -#     where 0 means no compression, 1 means the best compression
> -#     speed, and 20 means best compression ratio which will consume
> -#     more CPU. Defaults to 1. (Since 5.0)
> -#
> -# @block-bitmap-mapping: Maps block nodes and bitmaps on them to
> -#     aliases for the purpose of dirty bitmap migration.  Such aliases
> -#     may for example be the corresponding names on the opposite site.
> -#     The mapping must be one-to-one, but not necessarily complete: On
> -#     the source, unmapped bitmaps and all bitmaps on unmapped nodes
> -#     will be ignored.  On the destination, encountering an unmapped
> -#     alias in the incoming migration stream will result in a report,
> -#     and all further bitmap migration data will then be discarded.
> -#     Note that the destination does not know about bitmaps it does
> -#     not receive, so there is no limitation or requirement regarding
> -#     the number of bitmaps received, or how they are named, or on
> -#     which nodes they are placed.  By default (when this parameter
> -#     has never been set), bitmap names are mapped to themselves.
> -#     Nodes are mapped to their block device name if there is one, and
> -#     to their node name otherwise.  (Since 5.2)
> -#
> -# @x-vcpu-dirty-limit-period: Periodic time (in milliseconds) of dirty
> -#     limit during live migration.  Should be in the range 1 to 1000ms.
> -#     Defaults to 1000ms.  (Since 8.1)
> -#
> -# @vcpu-dirty-limit: Dirtyrate limit (MB/s) during live migration.
> -#     Defaults to 1.  (Since 8.1)
> -#
> -# Features:
> -#
> -# @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period
> -#     are experimental.
> -#
> -# TODO: either fuse back into MigrationParameters, or make
> -#     MigrationParameters members mandatory
> -#
> -# Since: 2.4
> -##
> -{ 'struct': 'MigrateSetParameters',
> -  'data': { '*announce-initial': 'size',
> -            '*announce-max': 'size',
> -            '*announce-rounds': 'size',
> -            '*announce-step': 'size',
> -            '*compress-level': 'uint8',
> -            '*compress-threads': 'uint8',
> -            '*compress-wait-thread': 'bool',
> -            '*decompress-threads': 'uint8',
> -            '*throttle-trigger-threshold': 'uint8',
> -            '*cpu-throttle-initial': 'uint8',
> -            '*cpu-throttle-increment': 'uint8',
> -            '*cpu-throttle-tailslow': 'bool',
> -            '*tls-creds': 'StrOrNull',
> -            '*tls-hostname': 'StrOrNull',
> -            '*tls-authz': 'StrOrNull',
> -            '*max-bandwidth': 'size',
> -            '*downtime-limit': 'uint64',
> -            '*x-checkpoint-delay': { 'type': 'uint32',
> -                                     'features': [ 'unstable' ] },
> -            '*block-incremental': 'bool',
> -            '*multifd-channels': 'uint8',
> -            '*xbzrle-cache-size': 'size',
> -            '*max-postcopy-bandwidth': 'size',
> -            '*max-cpu-throttle': 'uint8',
> -            '*multifd-compression': 'MultiFDCompression',
> -            '*multifd-zlib-level': 'uint8',
> -            '*multifd-zstd-level': 'uint8',
> -            '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ],
> -            '*x-vcpu-dirty-limit-period': { 'type': 'uint64',
> -                                            'features': [ 'unstable' ] },
> -            '*vcpu-dirty-limit': 'uint64'} }
> -
>  ##
>  # @migrate-set-parameters:
>  #
> @@ -1048,7 +865,7 @@
>  # <- { "return": {} }
>  ##
>  { 'command': 'migrate-set-parameters', 'boxed': true,
> -  'data': 'MigrateSetParameters' }
> +  'data': 'MigrationParameters' }
>  
>  ##
>  # @MigrationParameters:
> @@ -1214,9 +1031,9 @@
>              '*cpu-throttle-initial': 'uint8',
>              '*cpu-throttle-increment': 'uint8',
>              '*cpu-throttle-tailslow': 'bool',
> -            '*tls-creds': 'str',
> -            '*tls-hostname': 'str',
> -            '*tls-authz': 'str',
> +            '*tls-creds': 'StrOrNull',
> +            '*tls-hostname': 'StrOrNull',
> +            '*tls-authz': 'StrOrNull',
>              '*max-bandwidth': 'size',
>              '*downtime-limit': 'uint64',
>              '*x-checkpoint-delay': { 'type': 'uint32',
> diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h
> index e1df08876c..3ae83d8390 100644
> --- a/include/hw/qdev-properties.h
> +++ b/include/hw/qdev-properties.h
> @@ -59,6 +59,7 @@ extern const PropertyInfo qdev_prop_uint64_checkmask;
>  extern const PropertyInfo qdev_prop_int64;
>  extern const PropertyInfo qdev_prop_size;
>  extern const PropertyInfo qdev_prop_string;
> +extern const PropertyInfo qdev_prop_str_or_null;
>  extern const PropertyInfo qdev_prop_on_off_auto;
>  extern const PropertyInfo qdev_prop_size32;
>  extern const PropertyInfo qdev_prop_arraylen;
> @@ -171,6 +172,8 @@ extern const PropertyInfo qdev_prop_link;
>      DEFINE_PROP_UNSIGNED(_n, _s, _f, _d, qdev_prop_size, uint64_t)
>  #define DEFINE_PROP_STRING(_n, _s, _f)             \
>      DEFINE_PROP(_n, _s, _f, qdev_prop_string, char*)
> +#define DEFINE_PROP_STR_OR_NULL(_n, _s, _f)             \
> +    DEFINE_PROP(_n, _s, _f, qdev_prop_str_or_null, StrOrNull *)
>  #define DEFINE_PROP_ON_OFF_AUTO(_n, _s, _f, _d) \
>      DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_on_off_auto, OnOffAuto)
>  #define DEFINE_PROP_SIZE32(_n, _s, _f, _d)                       \
> diff --git a/migration/options.h b/migration/options.h
> index 045e2a41a2..124a5d450f 100644
> --- a/migration/options.h
> +++ b/migration/options.h
> @@ -56,6 +56,7 @@ bool migrate_zero_copy_send(void);
>  
>  bool migrate_multifd_flush_after_each_section(void);
>  bool migrate_postcopy(void);
> +/* Check whether TLS is enabled for migration */

Unrelated :)

>  bool migrate_tls(void);
>  
>  /* capabilities helpers */
> @@ -90,6 +91,8 @@ const char *migrate_tls_authz(void);
>  const char *migrate_tls_creds(void);
>  const char *migrate_tls_hostname(void);
>  uint64_t migrate_xbzrle_cache_size(void);
> +StrOrNull *StrOrNull_from_str(const char *str);
> +const char *str_from_StrOrNull(StrOrNull *obj);
>  
>  /* parameters setters */
>  
> diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
> index 357b8761b5..b4bbb52ae9 100644
> --- a/hw/core/qdev-properties.c
> +++ b/hw/core/qdev-properties.c
> @@ -2,6 +2,7 @@
>  #include "hw/qdev-properties.h"
>  #include "qapi/error.h"
>  #include "qapi/qapi-types-misc.h"
> +#include "qapi/qapi-visit-misc.h"
>  #include "qapi/qmp/qerror.h"
>  #include "qemu/ctype.h"
>  #include "qemu/error-report.h"
> @@ -490,6 +491,45 @@ const PropertyInfo qdev_prop_string = {
>      .set   = set_string,
>  };
>  
> +/* --- StrOrNull --- */
> +
> +static void release_str_or_null(Object *obj, const char *name, void *opaque)
> +{
> +    Property *prop = opaque;
> +
> +    qapi_free_StrOrNull(*(StrOrNull **)object_field_prop_ptr(obj, prop));
> +}
> +
> +static void get_str_or_null(Object *obj, Visitor *v, const char *name,
> +                            void *opaque, Error **errp)
> +{
> +    Property *prop = opaque;
> +    StrOrNull **ptr = object_field_prop_ptr(obj, prop);
> +
> +    visit_type_StrOrNull(v, name, ptr, errp);
> +}
> +
> +static void set_str_or_null(Object *obj, Visitor *v, const char *name,
> +                            void *opaque, Error **errp)
> +{
> +    Property *prop = opaque;
> +    StrOrNull **ptr = object_field_prop_ptr(obj, prop);
> +    StrOrNull *son;
> +
> +    if (!visit_type_StrOrNull(v, name, &son, errp)) {
> +        return;
> +    }
> +    qapi_free_StrOrNull(*ptr);
> +    *ptr = son;
> +}
> +
> +const PropertyInfo qdev_prop_str_or_null = {
> +    .name  = "StrOrNull",
> +    .release = release_str_or_null,
> +    .get   = get_str_or_null,
> +    .set   = set_str_or_null,
> +};
> +
>  /* --- on/off/auto --- */
>  
>  const PropertyInfo qdev_prop_on_off_auto = {
> diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c
> index c115ef2d23..88a8ccb475 100644
> --- a/migration/migration-hmp-cmds.c
> +++ b/migration/migration-hmp-cmds.c

Missing #include "migration/options.h".  Next patch unbreaks the build.

> @@ -257,6 +257,7 @@ void hmp_info_migrate_capabilities(Monitor *mon, const 
> QDict *qdict)
>  void hmp_info_migrate_parameters(Monitor *mon, const QDict *qdict)
>  {
>      MigrationParameters *params;
> +    const char *str;
>  
>      params = qmp_query_migrate_parameters(NULL);
>  
> @@ -309,14 +310,18 @@ void hmp_info_migrate_parameters(Monitor *mon, const 
> QDict *qdict)
>          monitor_printf(mon, "%s: %u\n",
>              MigrationParameter_str(MIGRATION_PARAMETER_MAX_CPU_THROTTLE),
>              params->max_cpu_throttle);
> -        assert(params->tls_creds);
> +        str = str_from_StrOrNull(params->tls_creds);
>          monitor_printf(mon, "%s: '%s'\n",
>              MigrationParameter_str(MIGRATION_PARAMETER_TLS_CREDS),
> -            params->tls_creds);
> -        assert(params->tls_hostname);
> +            str ? str : "");
> +        str = str_from_StrOrNull(params->tls_hostname);
>          monitor_printf(mon, "%s: '%s'\n",
>              MigrationParameter_str(MIGRATION_PARAMETER_TLS_HOSTNAME),
> -            params->tls_hostname);
> +            str ? str : "");
> +        str = str_from_StrOrNull(params->tls_authz);
> +        monitor_printf(mon, "%s: '%s'\n",
> +            MigrationParameter_str(MIGRATION_PARAMETER_TLS_AUTHZ),
> +            str ? str : "");
>          assert(params->has_max_bandwidth);
>          monitor_printf(mon, "%s: %" PRIu64 " bytes/second\n",
>              MigrationParameter_str(MIGRATION_PARAMETER_MAX_BANDWIDTH),
> @@ -345,9 +350,6 @@ void hmp_info_migrate_parameters(Monitor *mon, const 
> QDict *qdict)
>          monitor_printf(mon, "%s: %" PRIu64 "\n",
>              
> MigrationParameter_str(MIGRATION_PARAMETER_MAX_POSTCOPY_BANDWIDTH),
>              params->max_postcopy_bandwidth);
> -        monitor_printf(mon, "%s: '%s'\n",
> -            MigrationParameter_str(MIGRATION_PARAMETER_TLS_AUTHZ),
> -            params->tls_authz);
>  
>          if (params->has_block_bitmap_mapping) {
>              const BitmapMigrationNodeAliasList *bmnal;
> @@ -497,7 +499,7 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict 
> *qdict)
>      const char *param = qdict_get_str(qdict, "parameter");
>      const char *valuestr = qdict_get_str(qdict, "value");
>      Visitor *v = string_input_visitor_new(valuestr);
> -    MigrateSetParameters *p = g_new0(MigrateSetParameters, 1);
> +    MigrationParameters *p = g_new0(MigrationParameters, 1);
>      uint64_t valuebw = 0;
>      uint64_t cache_size;
>      Error *err = NULL;
> @@ -657,7 +659,7 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict 
> *qdict)
>      qmp_migrate_set_parameters(p, &err);
>  
>   cleanup:
> -    qapi_free_MigrateSetParameters(p);
> +    qapi_free_MigrationParameters(p);
>      visit_free(v);
>      hmp_handle_error(mon, err);
>  }
> diff --git a/migration/options.c b/migration/options.c
> index 6bbfd4853d..12e392f68c 100644
> --- a/migration/options.c
> +++ b/migration/options.c
> @@ -164,9 +164,12 @@ Property migration_properties[] = {
>      DEFINE_PROP_SIZE("announce-step", MigrationState,
>                        parameters.announce_step,
>                        DEFAULT_MIGRATE_ANNOUNCE_STEP),
> -    DEFINE_PROP_STRING("tls-creds", MigrationState, parameters.tls_creds),
> -    DEFINE_PROP_STRING("tls-hostname", MigrationState, 
> parameters.tls_hostname),
> -    DEFINE_PROP_STRING("tls-authz", MigrationState, parameters.tls_authz),
> +    DEFINE_PROP_STR_OR_NULL("tls-creds", MigrationState,
> +                            parameters.tls_creds),
> +    DEFINE_PROP_STR_OR_NULL("tls-hostname", MigrationState,
> +                            parameters.tls_hostname),
> +    DEFINE_PROP_STR_OR_NULL("tls-authz", MigrationState,
> +                            parameters.tls_authz),

The qdev machinery now additionally accepts JSON null as property
value.

If that's undesirable, we need to reject it.

If it's desirable, we need to document it, and we should probably make
it a separate patch.

To answer the question whether it's desirable, we need to recall the
purpose of the properties.  They go back to

commit e5cb7e7677010f529d3f0f9dcdb385dea9446f8d
Author: Peter Xu <peterx@redhat.com>
Date:   Tue Jun 27 12:10:13 2017 +0800

    migration: let MigrationState be a qdev
    
    Let the old man "MigrationState" join the object family. Direct benefit
    is that we can start to use all the property features derived from
    current QDev, like: HW_COMPAT_* bits, command line setup for migration
    parameters (so will never need to set them up each time using HMP/QMP,
    this is really, really attractive for test writters), etc.
    
    I see no reason to disallow this happen yet. So let's start from this
    one, to see whether it would be anything good.
    
    Now we init the MigrationState struct statically in main() to make sure
    it's initialized after global properties are applied, since we'll use
    them during creation of the object.
    
    No functional change at all.
    
    Reviewed-by: Juan Quintela <quintela@redhat.com>
    Signed-off-by: Peter Xu <peterx@redhat.com>
    Message-Id: <1498536619-14548-5-git-send-email-peterx@redhat.com>
    Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
    Signed-off-by: Juan Quintela <quintela@redhat.com>

>      DEFINE_PROP_UINT64("x-vcpu-dirty-limit-period", MigrationState,
>                         parameters.x_vcpu_dirty_limit_period,
>                         DEFAULT_MIGRATE_VCPU_DIRTY_LIMIT_PERIOD),
> @@ -201,6 +204,38 @@ Property migration_properties[] = {
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> +/*
> + * NOTE: here we have a trick when converting the empty string (""): we
> + * need to make sure the empty string ("") will be converted to NULL, as
> + * some TLS code may rely on that to detect whether something is enabled
> + * (e.g., the tls_authz field).

Suggest

    * Map JSON null and JSON "" to NULL, other JSON strings to the string.
    * The curious special treatment of "" is necessary, because it needs
    * to be interpreted like JSON null for backward compatibility.

> + */
> +const char *str_from_StrOrNull(StrOrNull *obj)
> +{
> +    if (!obj || obj->type == QTYPE_QNULL) {
> +        return NULL;
> +    } else if (obj->type == QTYPE_QSTRING) {
> +        if (obj->u.s[0] == '\0') {
> +            return NULL;
> +        } else {
> +            return obj->u.s;
> +        }
> +    } else {
> +        abort();
> +    }
> +}
> +
> +StrOrNull *StrOrNull_from_str(const char *str)
> +{
> +    StrOrNull *obj = g_new0(StrOrNull, 1);
> +
> +    assert(str);
> +    obj->type = QTYPE_QSTRING;
> +    obj->u.s = g_strdup(str);
> +
> +    return obj;
> +}
> +
>  bool migrate_auto_converge(void)
>  {
>      MigrationState *s = migrate_get_current();
> @@ -378,9 +413,11 @@ bool migrate_postcopy(void)
>  
>  bool migrate_tls(void)
>  {
> -    MigrationState *s = migrate_get_current();
> -
> -    return s->parameters.tls_creds && *s->parameters.tls_creds;
> +    /*
> +     * The whole TLS feature relies on a non-empty tls-creds set first.
> +     * It's disabled otherwise.
> +     */

Suggest

       /* TLS is enabled when @tls-creds is non-null */
  
> +    return migrate_tls_creds();
>  }
>  
>  typedef enum WriteTrackingSupport {
> @@ -827,21 +864,21 @@ const char *migrate_tls_authz(void)
>  {
>      MigrationState *s = migrate_get_current();
>  
> -    return s->parameters.tls_authz;
> +    return str_from_StrOrNull(s->parameters.tls_authz);
>  }

This maps "" to null on use of .tls_authz.  Direct use is wrong.

The alternative is to map it when it's set.  Then setting it must go
through a setter that maps, and direct use is fine.  Observation, not a
demand.

>  
>  const char *migrate_tls_creds(void)
>  {
>      MigrationState *s = migrate_get_current();
>  
> -    return s->parameters.tls_creds;
> +    return str_from_StrOrNull(s->parameters.tls_creds);
>  }
>  
>  const char *migrate_tls_hostname(void)
>  {
>      MigrationState *s = migrate_get_current();
>  
> -    return s->parameters.tls_hostname;
> +    return str_from_StrOrNull(s->parameters.tls_hostname);
>  }

Likewise.

>  
>  uint64_t migrate_xbzrle_cache_size(void)
> @@ -911,10 +948,9 @@ MigrationParameters *qmp_query_migrate_parameters(Error 
> **errp)
>      params->cpu_throttle_increment = s->parameters.cpu_throttle_increment;
>      params->has_cpu_throttle_tailslow = true;
>      params->cpu_throttle_tailslow = s->parameters.cpu_throttle_tailslow;
> -    params->tls_creds = g_strdup(s->parameters.tls_creds);
> -    params->tls_hostname = g_strdup(s->parameters.tls_hostname);
> -    params->tls_authz = g_strdup(s->parameters.tls_authz ?
> -                                 s->parameters.tls_authz : "");
> +    params->tls_creds = QAPI_CLONE(StrOrNull, s->parameters.tls_creds);
> +    params->tls_hostname = QAPI_CLONE(StrOrNull, s->parameters.tls_hostname);
> +    params->tls_authz = QAPI_CLONE(StrOrNull, s->parameters.tls_authz);
>      params->has_max_bandwidth = true;
>      params->max_bandwidth = s->parameters.max_bandwidth;
>      params->has_downtime_limit = true;
> @@ -963,8 +999,9 @@ MigrationParameters *qmp_query_migrate_parameters(Error 
> **errp)
>  
>  void migrate_params_init(MigrationParameters *params)
>  {
> -    params->tls_hostname = g_strdup("");
> -    params->tls_creds = g_strdup("");
> +    params->tls_hostname = StrOrNull_from_str("");
> +    params->tls_creds = StrOrNull_from_str("");
> +    params->tls_authz = StrOrNull_from_str("");
>  
>      /* Set has_* up only for parameter checks */
>      params->has_compress_level = true;
> @@ -1145,7 +1182,7 @@ bool migrate_params_check(MigrationParameters *params, 
> Error **errp)
>  #ifdef CONFIG_LINUX
>      if (migrate_zero_copy_send() &&
>          ((params->has_multifd_compression && params->multifd_compression) ||
> -         (params->tls_creds && *params->tls_creds))) {
> +         migrate_tls())) {

Correct only if params == current_migration!  Are they equal?

>          error_setg(errp,
>                     "Zero copy only available for non-compressed non-TLS 
> multifd migration");
>          return false;
> @@ -1172,113 +1209,7 @@ bool migrate_params_check(MigrationParameters 
> *params, Error **errp)
>      return true;
>  }
>  
> -static void migrate_params_test_apply(MigrateSetParameters *params,
> -                                      MigrationParameters *dest)
> -{
> -    *dest = migrate_get_current()->parameters;
> -
> -    /* TODO use QAPI_CLONE() instead of duplicating it inline */
> -
> -    if (params->has_compress_level) {
> -        dest->compress_level = params->compress_level;
> -    }
> -
> -    if (params->has_compress_threads) {
> -        dest->compress_threads = params->compress_threads;
> -    }
> -
> -    if (params->has_compress_wait_thread) {
> -        dest->compress_wait_thread = params->compress_wait_thread;
> -    }
> -
> -    if (params->has_decompress_threads) {
> -        dest->decompress_threads = params->decompress_threads;
> -    }
> -
> -    if (params->has_throttle_trigger_threshold) {
> -        dest->throttle_trigger_threshold = 
> params->throttle_trigger_threshold;
> -    }
> -
> -    if (params->has_cpu_throttle_initial) {
> -        dest->cpu_throttle_initial = params->cpu_throttle_initial;
> -    }
> -
> -    if (params->has_cpu_throttle_increment) {
> -        dest->cpu_throttle_increment = params->cpu_throttle_increment;
> -    }
> -
> -    if (params->has_cpu_throttle_tailslow) {
> -        dest->cpu_throttle_tailslow = params->cpu_throttle_tailslow;
> -    }
> -
> -    if (params->tls_creds) {
> -        assert(params->tls_creds->type == QTYPE_QSTRING);
> -        dest->tls_creds = params->tls_creds->u.s;
> -    }
> -
> -    if (params->tls_hostname) {
> -        assert(params->tls_hostname->type == QTYPE_QSTRING);
> -        dest->tls_hostname = params->tls_hostname->u.s;
> -    }
> -
> -    if (params->has_max_bandwidth) {
> -        dest->max_bandwidth = params->max_bandwidth;
> -    }
> -
> -    if (params->has_downtime_limit) {
> -        dest->downtime_limit = params->downtime_limit;
> -    }
> -
> -    if (params->has_x_checkpoint_delay) {
> -        dest->x_checkpoint_delay = params->x_checkpoint_delay;
> -    }
> -
> -    if (params->has_block_incremental) {
> -        dest->block_incremental = params->block_incremental;
> -    }
> -    if (params->has_multifd_channels) {
> -        dest->multifd_channels = params->multifd_channels;
> -    }
> -    if (params->has_multifd_compression) {
> -        dest->multifd_compression = params->multifd_compression;
> -    }
> -    if (params->has_xbzrle_cache_size) {
> -        dest->xbzrle_cache_size = params->xbzrle_cache_size;
> -    }
> -    if (params->has_max_postcopy_bandwidth) {
> -        dest->max_postcopy_bandwidth = params->max_postcopy_bandwidth;
> -    }
> -    if (params->has_max_cpu_throttle) {
> -        dest->max_cpu_throttle = params->max_cpu_throttle;
> -    }
> -    if (params->has_announce_initial) {
> -        dest->announce_initial = params->announce_initial;
> -    }
> -    if (params->has_announce_max) {
> -        dest->announce_max = params->announce_max;
> -    }
> -    if (params->has_announce_rounds) {
> -        dest->announce_rounds = params->announce_rounds;
> -    }
> -    if (params->has_announce_step) {
> -        dest->announce_step = params->announce_step;
> -    }
> -
> -    if (params->has_block_bitmap_mapping) {
> -        dest->has_block_bitmap_mapping = true;
> -        dest->block_bitmap_mapping = params->block_bitmap_mapping;
> -    }
> -
> -    if (params->has_x_vcpu_dirty_limit_period) {
> -        dest->x_vcpu_dirty_limit_period =
> -            params->x_vcpu_dirty_limit_period;
> -    }
> -    if (params->has_vcpu_dirty_limit) {
> -        dest->vcpu_dirty_limit = params->vcpu_dirty_limit;
> -    }
> -}

I believe your commit message tries to explain why this function is no
longer needed.  But it's still not obvious to me.

I suspect this patch is doing too much.

> -
> -static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
> +static void migrate_params_apply(MigrationParameters *params, Error **errp)
>  {
>      MigrationState *s = migrate_get_current();
>  
> @@ -1317,21 +1248,18 @@ static void migrate_params_apply(MigrateSetParameters 
> *params, Error **errp)
>      }
>  
>      if (params->tls_creds) {
> -        g_free(s->parameters.tls_creds);
> -        assert(params->tls_creds->type == QTYPE_QSTRING);
> -        s->parameters.tls_creds = g_strdup(params->tls_creds->u.s);
> +        qapi_free_StrOrNull(s->parameters.tls_creds);
> +        s->parameters.tls_creds = QAPI_CLONE(StrOrNull, params->tls_creds);
>      }
>  
>      if (params->tls_hostname) {
> -        g_free(s->parameters.tls_hostname);
> -        assert(params->tls_hostname->type == QTYPE_QSTRING);
> -        s->parameters.tls_hostname = g_strdup(params->tls_hostname->u.s);
> +        qapi_free_StrOrNull(s->parameters.tls_hostname);
> +        s->parameters.tls_hostname = QAPI_CLONE(StrOrNull, 
> params->tls_hostname);
>      }
>  
>      if (params->tls_authz) {
> -        g_free(s->parameters.tls_authz);
> -        assert(params->tls_authz->type == QTYPE_QSTRING);
> -        s->parameters.tls_authz = g_strdup(params->tls_authz->u.s);
> +        qapi_free_StrOrNull(s->parameters.tls_authz);
> +        s->parameters.tls_authz = QAPI_CLONE(StrOrNull, params->tls_authz);
>      }
>  
>      if (params->has_max_bandwidth) {
> @@ -1404,33 +1332,9 @@ static void migrate_params_apply(MigrateSetParameters 
> *params, Error **errp)
>      }
>  }
>  
> -void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp)
> +void qmp_migrate_set_parameters(MigrationParameters *params, Error **errp)
>  {
> -    MigrationParameters tmp;
> -
> -    /* TODO Rewrite "" to null instead for all three tls_* parameters */
> -    if (params->tls_creds
> -        && params->tls_creds->type == QTYPE_QNULL) {
> -        qobject_unref(params->tls_creds->u.n);
> -        params->tls_creds->type = QTYPE_QSTRING;
> -        params->tls_creds->u.s = strdup("");
> -    }
> -    if (params->tls_hostname
> -        && params->tls_hostname->type == QTYPE_QNULL) {
> -        qobject_unref(params->tls_hostname->u.n);
> -        params->tls_hostname->type = QTYPE_QSTRING;
> -        params->tls_hostname->u.s = strdup("");
> -    }
> -    if (params->tls_authz
> -        && params->tls_authz->type == QTYPE_QNULL) {
> -        qobject_unref(params->tls_authz->u.n);
> -        params->tls_authz->type = QTYPE_QSTRING;
> -        params->tls_authz->u.s = strdup("");
> -    }
> -
> -    migrate_params_test_apply(params, &tmp);
> -
> -    if (!migrate_params_check(&tmp, errp)) {
> +    if (!migrate_params_check(params, errp)) {
>          /* Invalid parameter */
>          return;
>      }
> diff --git a/migration/tls.c b/migration/tls.c
> index fa03d9136c..c2ed4ff557 100644
> --- a/migration/tls.c
> +++ b/migration/tls.c
> @@ -126,7 +126,8 @@ QIOChannelTLS *migration_tls_client_create(QIOChannel 
> *ioc,
>      }
>  
>      const char *tls_hostname = migrate_tls_hostname();
> -    if (tls_hostname && *tls_hostname) {
> +    /* If tls_hostname, then it must be non-empty string already */

I'm not sure the comment makes sense outside this commit's context.

> +    if (tls_hostname) {
>          hostname = tls_hostname;
>      }