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Re: [RFC PATCH v3 4/4] hw/arm/virt: Parse -smp cluster parameter in virt
From: |
Andrew Jones |
Subject: |
Re: [RFC PATCH v3 4/4] hw/arm/virt: Parse -smp cluster parameter in virt_smp_parse |
Date: |
Tue, 18 May 2021 10:19:53 +0200 |
On Tue, May 18, 2021 at 11:48:34AM +0800, wangyanan (Y) wrote:
> Hi Salil,
>
> On 2021/5/17 23:17, Salil Mehta wrote:
> > > 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?
> The smp_clusters is added in VirtMachineState and nowhere else because
> it's currently only used for ARM. But I think maybe I should also move it to
> CpuTopology structure like [1] is doing to move dies to CpuTopology.
Yes, please do that.
Thanks,
drew
>
> Move clusters to CpuTopology won't affect other architectures that don't
> support it yet, and will also make it easy if they want to in the future.
>
> [1] From Paolo:
> https://patchwork.kernel.org/project/qemu-devel/patch/20210513162901.1310239-10-pbonzini@redhat.com/
>
> Thanks,
> Yanan
> > Salil.
> >
> > > ms->smp.cores = cores;
> > > ms->smp.threads = threads;
> > > }
> > .
>