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machine: Set the value of cpus to match maxcpus if it's omitted

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Currently we directly calculate the omitted cpus based on the given
incomplete collection of parameters. This makes some cmdlines like:
  -smp maxcpus=16
  -smp sockets=2,maxcpus=16
  -smp sockets=2,dies=2,maxcpus=16
  -smp sockets=2,cores=4,maxcpus=16
not work. We should probably set the value of cpus to match maxcpus
if it's omitted, which will make above configs start to work.

So the calculation logic of cpus/maxcpus after this patch will be:
When both maxcpus and cpus are omitted, maxcpus will be calculated
from the given parameters and cpus will be set equal to maxcpus.
When only one of maxcpus and cpus is given then the omitted one
will be set to its counterpart's value. Both maxcpus and cpus may
be specified, but maxcpus must be equal to or greater than cpus.

Note: change in this patch won't affect any existing working cmdlines
but allows more incomplete configs to be valid.

Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210929025816.21076-6-wangyanan55@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Yanan Wang 2021-09-29 10:58:05 +08:00 committed by Paolo Bonzini
parent 9a52b50806
commit 7d8c5a3962
3 changed files with 40 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
hw/core/machine.c
View File

@ -760,15 +760,14 @@ static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
}
/* compute missing values, prefer sockets over cores over threads */
maxcpus = maxcpus > 0 ? maxcpus : cpus;
if (cpus == 0) {
if (cpus == 0 && maxcpus == 0) {
sockets = sockets > 0 ? sockets : 1;
cores = cores > 0 ? cores : 1;
threads = threads > 0 ? threads : 1;
cpus = sockets * cores * threads;
} else {
maxcpus = maxcpus > 0 ? maxcpus : cpus;
} else if (sockets == 0) {
if (sockets == 0) {
cores = cores > 0 ? cores : 1;
threads = threads > 0 ? threads : 1;
sockets = maxcpus / (cores * threads);
@ -778,6 +777,10 @@ static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
} else if (threads == 0) {
threads = maxcpus / (sockets * cores);
}
}
maxcpus = maxcpus > 0 ? maxcpus : sockets * cores * threads;
cpus = cpus > 0 ? cpus : maxcpus;
if (sockets * cores * threads < cpus) {
error_setg(errp, "cpu topology: "

13
hw/i386/pc.c
View File

@ -727,15 +727,14 @@ static void pc_smp_parse(MachineState *ms, SMPConfiguration *config, Error **err
dies = dies > 0 ? dies : 1;
/* compute missing values, prefer sockets over cores over threads */
maxcpus = maxcpus > 0 ? maxcpus : cpus;
if (cpus == 0) {
if (cpus == 0 && maxcpus == 0) {
sockets = sockets > 0 ? sockets : 1;
cores = cores > 0 ? cores : 1;
threads = threads > 0 ? threads : 1;
cpus = sockets * dies * cores * threads;
} else {
maxcpus = maxcpus > 0 ? maxcpus : cpus;
} else if (sockets == 0) {
if (sockets == 0) {
cores = cores > 0 ? cores : 1;
threads = threads > 0 ? threads : 1;
sockets = maxcpus / (dies * cores * threads);
@ -745,6 +744,10 @@ static void pc_smp_parse(MachineState *ms, SMPConfiguration *config, Error **err
} else if (threads == 0) {
threads = maxcpus / (sockets * dies * cores);
}
}
maxcpus = maxcpus > 0 ? maxcpus : sockets * dies * cores * threads;
cpus = cpus > 0 ? cpus : maxcpus;
if (sockets * dies * cores * threads < cpus) {
error_setg(errp, "cpu topology: "

11
qemu-options.hx
View File

@ -220,9 +220,14 @@ SRST
Simulate a SMP system with '\ ``n``\ ' CPUs initially present on
the machine type board. On boards supporting CPU hotplug, the optional
'\ ``maxcpus``\ ' parameter can be set to enable further CPUs to be
added at runtime. If omitted the maximum number of CPUs will be
set to match the initial CPU count. Both parameters are subject to
an upper limit that is determined by the specific machine type chosen.
added at runtime. When both parameters are omitted, the maximum number
of CPUs will be calculated from the provided topology members and the
initial CPU count will match the maximum number. When only one of them
is given then the omitted one will be set to its counterpart's value.
Both parameters may be specified, but the maximum number of CPUs must
be equal to or greater than the initial CPU count. Both parameters are
subject to an upper limit that is determined by the specific machine
type chosen.
To control reporting of CPU topology information, the number of sockets,
dies per socket, cores per die, and threads per core can be specified.