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>
---
hw/core/machine.c | 29 ++++++++++++++++-------------
hw/i386/pc.c | 29 ++++++++++++++++-------------
qemu-options.hx | 11 ++++++++---
3 files changed, 40 insertions(+), 29 deletions(-)
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 69979c93dd..958e6e7107 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -755,25 +755,28 @@ 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) {
- cores = cores > 0 ? cores : 1;
- threads = threads > 0 ? threads : 1;
- sockets = maxcpus / (cores * threads);
- } else if (cores == 0) {
- threads = threads > 0 ? threads : 1;
- cores = maxcpus / (sockets * threads);
- } else if (threads == 0) {
- threads = maxcpus / (sockets * cores);
+
+ if (sockets == 0) {
+ cores = cores > 0 ? cores : 1;
+ threads = threads > 0 ? threads : 1;
+ sockets = maxcpus / (cores * threads);
+ } else if (cores == 0) {
+ threads = threads > 0 ? threads : 1;
+ cores = maxcpus / (sockets * threads);
+ } 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: "
"sockets (%u) * cores (%u) * threads (%u) < "
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index a9ff9ef52c..9ad7ae5254 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -725,25 +725,28 @@ 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) {
- cores = cores > 0 ? cores : 1;
- threads = threads > 0 ? threads : 1;
- sockets = maxcpus / (dies * cores * threads);
- } else if (cores == 0) {
- threads = threads > 0 ? threads : 1;
- cores = maxcpus / (sockets * dies * threads);
- } else if (threads == 0) {
- threads = maxcpus / (sockets * dies * cores);
+
+ if (sockets == 0) {
+ cores = cores > 0 ? cores : 1;
+ threads = threads > 0 ? threads : 1;
+ sockets = maxcpus / (dies * cores * threads);
+ } else if (cores == 0) {
+ threads = threads > 0 ? threads : 1;
+ cores = maxcpus / (sockets * dies * threads);
+ } 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: "
"sockets (%u) * dies (%u) * cores (%u) * threads (%u) < "
diff --git a/qemu-options.hx b/qemu-options.hx
index e077aa80bf..0912236b4b 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -210,9 +210,14 @@ 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
+ equal to or greater than the initial CPU count. Both parameters are