[Linuxarm] Re: [RFC PATCH v3 4/4] hw/arm/virt: Parse -smp cluster parameter in virt_smp_parse

From: Qemu-devel [mailto:qemu-devel-bounces+salil.mehta=huawei.com@nongnu.org] On Behalf Of Yanan Wang Sent: Sunday, May 16, 2021 11:32 AM To: Peter Maydell peter.maydell@linaro.org; Paolo Bonzini pbonzini@redhat.com; Andrew Jones drjones@redhat.com; Michael S . Tsirkin mst@redhat.com; Igor Mammedov imammedo@redhat.com; Shannon Zhao shannon.zhaosl@gmail.com; qemu-devel@nongnu.org; qemu-arm@nongnu.org Cc: Song Bao Hua (Barry Song) song.bao.hua@hisilicon.com; Philippe Mathieu-Daudé philmd@redhat.com; wangyanan (Y) wangyanan55@huawei.com; Zengtao (B) prime.zeng@hisilicon.com; Wanghaibin (D) wanghaibin.wang@huawei.com; yuzenghui yuzenghui@huawei.com; yangyicong yangyicong@huawei.com; zhukeqian zhukeqian1@huawei.com Subject: [RFC PATCH v3 4/4] hw/arm/virt: Parse -smp cluster parameter in virt_smp_parse

There is a separate function virt_smp_parse() in hw/virt/arm.c used to parse cpu topology for the ARM machines. So add parsing of -smp cluster parameter in it, then total number of logical cpus will be calculated like: max_cpus = sockets * clusters * cores * threads.

Note, we will assume multi-cluster in one socket is not supported and default the value of clusters to 1, if it's not explicitly specified in -smp cmdline.

Signed-off-by: Yanan Wang wangyanan55@huawei.com

hw/arm/virt.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c index 7de822e491..678d5ef36c 100644 --- a/hw/arm/virt.c +++ b/hw/arm/virt.c @@ -2642,8 +2642,8 @@ static int virt_kvm_type(MachineState *ms, const char *type_str)

• with the -smp cmdlines when parsing them.
• We require that at least one of cpus or maxcpus must be provided.

• • Threads will default to 1 if not provided. Sockets and cores must
• • be either both provided or both not.

• • Clusters and threads will default to 1 if they are not provided.
• • Sockets and cores must be either both provided or both not.
  • Note, if neither sockets nor cores are specified, we will calculate
  • all the missing values just like smp_parse() does, but will disable

@@ -2652,15 +2652,18 @@ static int virt_kvm_type(MachineState *ms, const char *type_str) static void virt_smp_parse(MachineState *ms, QemuOpts *opts) { VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(ms);

• VirtMachineState *vms = VIRT_MACHINE(ms);

  if (opts) { unsigned cpus = qemu_opt_get_number(opts, "cpus", 0); unsigned maxcpus = qemu_opt_get_number(opts, "maxcpus", 0); unsigned sockets = qemu_opt_get_number(opts, "sockets", 0);

•    unsigned clusters = qemu_opt_get_number(opts, "clusters", 0);
     unsigned cores = qemu_opt_get_number(opts, "cores", 0);
     unsigned threads = qemu_opt_get_number(opts, "threads", 0);
  
  

•    /* Default threads to 1 if not provided */
  

•    /* Default clusters and threads to 1 if not provided */
  

•    clusters = clusters > 0 ? clusters : 1;
     threads = threads > 0 ? threads : 1;
  
     if (cpus == 0 && maxcpus == 0) {
  

@@ -2676,13 +2679,13 @@ static void virt_smp_parse(MachineState *ms, QemuOpts *opts) cores = 1; if (cpus == 0) { sockets = 1;

•            cpus = sockets * cores * threads;
  

•            cpus = sockets * clusters * cores * threads;
         } else {
             maxcpus = maxcpus > 0 ? maxcpus : cpus;
  

•            sockets = maxcpus / (cores * threads);
  

•            sockets = maxcpus / (clusters * cores * threads);
         }
     } else if (sockets > 0 && cores > 0) {
  

•        cpus = cpus > 0 ? cpus : sockets * cores * threads;
  

•        cpus = cpus > 0 ? cpus : sockets * clusters * cores * threads;
         maxcpus = maxcpus > 0 ? maxcpus : cpus;
     } else {
         error_report("sockets and cores must be both provided "
  

@@ -2695,25 +2698,26 @@ static void virt_smp_parse(MachineState *ms, QemuOpts *opts) exit(1); }

•    if (sockets * cores * threads < cpus) {
  

•    if (sockets * clusters * cores * threads < cpus) {
         error_report("cpu topology: "
  

•                     "sockets (%u) * cores (%u) * threads (%u) < "
  

•                     "smp_cpus (%u)",
  

•                     sockets, cores, threads, cpus);
  

•                     "sockets (%u) * clusters (%u) * cores (%u) * "
  

•                     "threads (%u) < smp_cpus (%u)",
  

•                     sockets, clusters, cores, threads, cpus);
         exit(1);
     }
  
  

•    if (sockets * cores * threads != maxcpus) {
  

•    if (sockets * clusters * cores * threads != maxcpus) {
         error_report("cpu topology: "
  

•                     "sockets (%u) * cores (%u) * threads (%u) "
  

•                     "!= maxcpus (%u)",
  

•                     sockets, cores, threads, maxcpus);
  

•                     "sockets (%u) * clusters (%u) * cores (%u) * "
  

•                     "threads (%u) != maxcpus (%u)",
  

•                     sockets, clusters, cores, threads, maxcpus);
         exit(1);
     }
  
     ms->smp.cpus = cpus;
     ms->smp.max_cpus = maxcpus;
     ms->smp.sockets = sockets;
  

•    vms->smp_clusters = clusters;
  

This variable naming *smp_clusters* looks out-of-sorts. I thought a similar variable *smp_cpus* was destined to be removed for the reason given in below link - a patch by Andrew Jones?

Link: https://lists.gnu.org/archive/html/qemu-arm/2020-12/msg00418.html

Am I missing anything here?

Salil.

     ms->smp.cores = cores;
     ms->smp.threads = threads;
 }