Re: [RFC PATCH 4/6] machine: Uniformly use maxcpus to calculate the missing values

[wangyanan (Y)]

On 2021/7/2 18:07, Yanan Wang wrote:
> We are currently using maxcpus to calculate value of sockets but using
> cpus to calculate value of cores/threads. This makes cmdlines like
> "-smp 8,maxcpus=12,cores=4" work while "-smp 8,maxcpus=12,sockets=3"
> break the invalid cpu topology check.
>
> This patch allows us to uniformly use maxcpus to calculate the missing
> values. Also the if branch of "cpus == 0 || sockets == 0" was splited
> into branches of "cpus == 0" and "sockets == 0" so that we can clearly
> figure out that we are parsing -smp cmdlines with a preference of cpus
> over sockets over cores over threads.
BTW, after this patch, configs like:
-smp maxcpus=16 --> -smp 1,sockets=1,cores=1,threads=1,maxcpus=16
-smp sockets=2,maxcpus=16 --> -smp 2,sockets=2,cores=1,threads=1,maxcpus=16
......
still can not work. So I suggest to use the parameters computed by 
maxcpus to calculate
the value of cpus if it's omitted. The diff based on this patch is:

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 93c5227920..924c48fd43 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -757,13 +757,7 @@ 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) {
-        sockets = sockets > 0 ? sockets : 1;
-        cores = cores > 0 ? cores : 1;
-        threads = threads > 0 ? threads : 1;
-        cpus = sockets * cores * threads;
-        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);
@@ -777,6 +771,9 @@ static void smp_parse(MachineState *ms, 
SMPConfiguration *config, Error **errp)
         threads = threads > 0 ? threads : 1;
     }

+    cpus = cpus > 0 ? cpus : sockets * cores * threads;
+    maxcpus = maxcpus > 0 ? maxcpus : cpus;
+
     if (sockets * cores * threads < cpus) {
         error_setg(errp, "cpu topology: "
                    "sockets (%u) * cores (%u) * threads (%u) < "


Thanks,
Yanan
.
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> ---
>   hw/core/machine.c | 36 +++++++++++++++++++-----------------
>   hw/i386/pc.c      | 37 +++++++++++++++++++------------------
>   2 files changed, 38 insertions(+), 35 deletions(-)
>
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 1e194677cd..58882835be 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -752,34 +752,36 @@ static void smp_parse(MachineState *ms, SMPConfiguration 
> *config, Error **errp)
>       }
>   
>       /* compute missing values, prefer sockets over cores over threads */
> -    if (cpus == 0 || sockets == 0) {
> +    maxcpus = maxcpus > 0 ? maxcpus : cpus;
> +
> +    if (cpus == 0) {
> +        sockets = sockets > 0 ? sockets : 1;
>           cores = cores > 0 ? cores : 1;
>           threads = threads > 0 ? threads : 1;
> -        if (cpus == 0) {
> -            sockets = sockets > 0 ? sockets : 1;
> -            cpus = cores * threads * sockets;
> -        } else {
> -            maxcpus = maxcpus > 0 ? maxcpus : cpus;
> -            sockets = maxcpus / (cores * threads);
> -            sockets = sockets > 0 ? sockets : 1;
> -        }
> +        cpus = sockets * cores * threads;
> +        maxcpus = maxcpus > 0 ? maxcpus : cpus;
> +    } else if (sockets == 0) {
> +        cores = cores > 0 ? cores : 1;
> +        threads = threads > 0 ? threads : 1;
> +        sockets = maxcpus / (cores * threads);
> +        sockets = sockets > 0 ? sockets : 1;
>       } else if (cores == 0) {
>           threads = threads > 0 ? threads : 1;
> -        cores = cpus / (sockets * threads);
> +        cores = maxcpus / (sockets * threads);
>           cores = cores > 0 ? cores : 1;
>       } else if (threads == 0) {
> -        threads = cpus / (cores * sockets);
> +        threads = maxcpus / (sockets * cores);
>           threads = threads > 0 ? threads : 1;
> -    } else if (sockets * cores * threads < cpus) {
> +    }
> +
> +    if (sockets * cores * threads < cpus) {
>           error_setg(errp, "cpu topology: "
> -                   "sockets (%u) * cores (%u) * threads (%u) < "
> -                   "smp_cpus (%u)",
> +                   "sockets (%u) * cores (%u) * threads (%u) "
> +                   "< smp_cpus (%u)",
>                      sockets, cores, threads, cpus);
>           return;
>       }
>   
> -    maxcpus = maxcpus > 0 ? maxcpus : cpus;
> -
>       if (maxcpus < cpus) {
>           error_setg(errp, "maxcpus must be equal to or greater than smp");
>           return;
> @@ -795,9 +797,9 @@ static void smp_parse(MachineState *ms, SMPConfiguration 
> *config, Error **errp)
>       }
>   
>       ms->smp.cpus = cpus;
> +    ms->smp.sockets = sockets;
>       ms->smp.cores = cores;
>       ms->smp.threads = threads;
> -    ms->smp.sockets = sockets;
>       ms->smp.max_cpus = maxcpus;
>   }
>   
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 93d1f12a49..1812f33ab1 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -721,35 +721,36 @@ static void pc_smp_parse(MachineState *ms, 
> SMPConfiguration *config, Error **err
>   
>       /* compute missing values, prefer sockets over cores over threads */
>       dies = dies > 0 ? dies : 1;
> +    maxcpus = maxcpus > 0 ? maxcpus : cpus;
>   
> -    if (cpus == 0 || sockets == 0) {
> +    if (cpus == 0) {
> +        sockets = sockets > 0 ? sockets : 1;
>           cores = cores > 0 ? cores : 1;
>           threads = threads > 0 ? threads : 1;
> -        if (cpus == 0) {
> -            sockets = sockets > 0 ? sockets : 1;
> -            cpus = cores * threads * dies * sockets;
> -        } else {
> -            maxcpus = maxcpus > 0 ? maxcpus : cpus;
> -            sockets = maxcpus / (dies * cores * threads);
> -            sockets = sockets > 0 ? sockets : 1;
> -        }
> +        cpus = sockets * dies * cores * threads;
> +        maxcpus = maxcpus > 0 ? maxcpus : cpus;
> +    } else if (sockets == 0) {
> +        cores = cores > 0 ? cores : 1;
> +        threads = threads > 0 ? threads : 1;
> +        sockets = maxcpus / (dies * cores * threads);
> +        sockets = sockets > 0 ? sockets : 1;
>       } else if (cores == 0) {
>           threads = threads > 0 ? threads : 1;
> -        cores = cpus / (sockets * dies * threads);
> +        cores = maxcpus / (sockets * dies * threads);
>           cores = cores > 0 ? cores : 1;
>       } else if (threads == 0) {
> -        threads = cpus / (cores * dies * sockets);
> +        threads = maxcpus / (sockets * dies * cores);
>           threads = threads > 0 ? threads : 1;
> -    } else if (sockets * dies * cores * threads < cpus) {
> +    }
> +
> +    if (sockets * dies * cores * threads < cpus) {
>           error_setg(errp, "cpu topology: "
> -                   "sockets (%u) * dies (%u) * cores (%u) * threads (%u) < "
> -                   "smp_cpus (%u)",
> +                   "sockets (%u) * dies (%u) * cores (%u) * threads (%u) "
> +                   "< smp_cpus (%u)",
>                      sockets, dies, cores, threads, cpus);
>           return;
>       }
>   
> -    maxcpus = maxcpus > 0 ? maxcpus : cpus;
> -
>       if (maxcpus < cpus) {
>           error_setg(errp, "maxcpus must be equal to or greater than smp");
>           return;
> @@ -765,10 +766,10 @@ static void pc_smp_parse(MachineState *ms, 
> SMPConfiguration *config, Error **err
>       }
>   
>       ms->smp.cpus = cpus;
> -    ms->smp.cores = cores;
> -    ms->smp.threads = threads;
>       ms->smp.sockets = sockets;
>       ms->smp.dies = dies;
> +    ms->smp.cores = cores;
> +    ms->smp.threads = threads;
>       ms->smp.max_cpus = maxcpus;
>   }
>