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machine: Deprecate "parameter=0" SMP configurations

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In the SMP configuration, we should either provide a topology
parameter with a reasonable value (greater than zero) or just
omit it and QEMU will compute the missing value.

The users shouldn't provide a configuration with any parameter
of it specified as zero (e.g. -smp 8,sockets=0) which could
possibly cause unexpected results in the -smp parsing. So we
deprecate this kind of configurations since 6.2 by adding the
explicit sanity check.

Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210929025816.21076-3-wangyanan55@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Yanan Wang 2021-09-29 10:58:02 +08:00 committed by Paolo Bonzini
parent 7237c7ce77
commit c2511b1632
3 changed files with 36 additions and 5 deletions
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15
docs/about/deprecated.rst
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@ -160,6 +160,21 @@ Use ``-display sdl`` instead.
Use ``-display curses`` instead.
``-smp`` ("parameter=0" SMP configurations) (since 6.2)
'''''''''''''''''''''''''''''''''''''''''''''''''''''''
Specified CPU topology parameters must be greater than zero.
In the SMP configuration, users should either provide a CPU topology
parameter with a reasonable value (greater than zero) or just omit it
and QEMU will compute the missing value.
However, historically it was implicitly allowed for users to provide
a parameter with zero value, which is meaningless and could also possibly
cause unexpected results in the -smp parsing. So support for this kind of
configurations (e.g. -smp 8,sockets=0) is deprecated since 6.2 and will
be removed in the near future, users have to ensure that all the topology
members described with -smp are greater than zero.
Plugin argument passing through ``arg=<string>`` (since 6.1)
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

14
hw/core/machine.c
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@ -835,6 +835,20 @@ static void machine_set_smp(Object *obj, Visitor *v, const char *name,
return;
}
/*
* Specified CPU topology parameters must be greater than zero,
* explicit configuration like "cpus=0" is not allowed.
*/
if ((config->has_cpus && config->cpus == 0) ||
(config->has_sockets && config->sockets == 0) ||
(config->has_dies && config->dies == 0) ||
(config->has_cores && config->cores == 0) ||
(config->has_threads && config->threads == 0) ||
(config->has_maxcpus && config->maxcpus == 0)) {
warn_report("Deprecated CPU topology (considered invalid): "
"CPU topology parameters must be greater than zero");
}
mc->smp_parse(ms, config, errp);
if (*errp) {
goto out_free;

12
qemu-options.hx
View File

@ -233,11 +233,13 @@ SRST
of computing the CPU maximum count.
Either the initial CPU count, or at least one of the topology parameters
must be specified. Values for any omitted parameters will be computed
from those which are given. Historically preference was given to the
coarsest topology parameters when computing missing values (ie sockets
preferred over cores, which were preferred over threads), however, this
behaviour is considered liable to change.
must be specified. The specified parameters must be greater than zero,
explicit configuration like "cpus=0" is not allowed. Values for any
omitted parameters will be computed from those which are given.
Historically preference was given to the coarsest topology parameters
when computing missing values (ie sockets preferred over cores, which
were preferred over threads), however, this behaviour is considered
liable to change.
ERST
DEF("numa", HAS_ARG, QEMU_OPTION_numa,