Re: [PATCH v4 1/1] RISC-V: Create unique identification for SoC PMU

[Nikita Shubin <nikita.shubin@maquefel.me>]

Hello Anup!

On Mon, 20 Jun 2022 12:40:20 -0700
Atish Patra <atishp@atishpatra.org> wrote:

> On Mon, Jun 20, 2022 at 7:40 AM Nikita Shubin
> <nikita.shubin@maquefel.me> wrote:
> >
> > On Mon, 20 Jun 2022 17:30:58 +0530
> > Anup Patel <apatel@ventanamicro.com> wrote:
> >  
> > > On Sun, Jun 19, 2022 at 4:41 PM Nikita Shubin
> > > <nikita.shubin@maquefel.me> wrote:  
> > > >
> > > > From: Nikita Shubin <n.shubin@yadro.com>
> > > >
> > > > Provide RISC-V SBI PMU id to distinguish different cores or
> > > > SoCs via "devices/platform/riscv-pmu/id" sysfs entry.
> > > >
> > > > The identification is generated as string of marchid, mimpid,
> > > > mvendorid in hex format separated by coma -
> > > > "0x70032,0x70032,0x0".
> > > >
> > > > The CSRs are detailed in the RISC-V privileged spec [1].
> > > > [1] https://github.com/riscv/riscv-isa-manual
> > > >
> > > > Inspired-by: João Mário Domingos <joao.mario@tecnico.ulisboa.pt>
> > > > Signed-off-by: Nikita Shubin <n.shubin@yadro.com>  
> > >
> > > The mvendorid, marchid, and mimpid can be useful to apps other
> > > than perf tool.
> > >
> > > I have tried to extend /proc/cpuinfo with this information which
> > > can be parsed by perf tool:
> > > https://lore.kernel.org/all/20220620115549.1529597-1-apatel@ventanamicro.com/
> > >  
> >
> > Atish, what do you think about this ?
> >
> > RISC-V perf can rely on "/proc/cpuinfo", in some similar manner like
> > "tools/perf/arch/s390/util/header.c" does.
> >  
> 
> Yes. We can expose these three values either in sysfs or procfs
> (/proc/cpuinfo). For perf tool, it shouldn't matter as the header.c
> will need to generate the unique cpuid
> string from either.
> 
> I am not sure if any other userspace tool prefers to parse sysfs
> instead of cpuinfo.

Okay - let's stick to /proc/cpuinfo.

> 
> > Can it create problems with pmu identification in case of
> > hetergenous harts ?
> >  
> 
> Does perf support hetergenous harts at all ? ARM64 code
> (tool/perf/arch/arm64/util/header.c)
> just breaks out of the loop after finding the first MIDR.
> 
> > >
> > > Regards,
> > > Anup
> > >  
> > > > ---
> > > > v3->v4:
> > > > - use string for pmuid
> > > > - rename pmu_sbi_id_show to id_show
> > > > - fix error print message in id_show
> > > > - fix DEVICE_ATTR to use octal permissions
> > > > ---
> > > >  arch/riscv/kernel/sbi.c        |  3 +++
> > > >  drivers/perf/riscv_pmu_sbi.c   | 41
> > > > ++++++++++++++++++++++++++++++++++
> > > > include/linux/perf/riscv_pmu.h | 1 + 3 files changed, 45
> > > > insertions(+)
> > > >
> > > > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> > > > index 775d3322b422..50dd9b6ecc9e 100644
> > > > --- a/arch/riscv/kernel/sbi.c
> > > > +++ b/arch/riscv/kernel/sbi.c
> > > > @@ -627,16 +627,19 @@ long sbi_get_mvendorid(void)
> > > >  {
> > > >         return __sbi_base_ecall(SBI_EXT_BASE_GET_MVENDORID);
> > > >  }
> > > > +EXPORT_SYMBOL(sbi_get_mvendorid);
> > > >
> > > >  long sbi_get_marchid(void)
> > > >  {
> > > >         return __sbi_base_ecall(SBI_EXT_BASE_GET_MARCHID);
> > > >  }
> > > > +EXPORT_SYMBOL(sbi_get_marchid);
> > > >
> > > >  long sbi_get_mimpid(void)
> > > >  {
> > > >         return __sbi_base_ecall(SBI_EXT_BASE_GET_MIMPID);
> > > >  }
> > > > +EXPORT_SYMBOL(sbi_get_mimpid);
> > > >
> > > >  static void sbi_send_cpumask_ipi(const struct cpumask *target)
> > > >  {
> > > > diff --git a/drivers/perf/riscv_pmu_sbi.c
> > > > b/drivers/perf/riscv_pmu_sbi.c index dca3537a8dcc..be812f855617
> > > > 100644 --- a/drivers/perf/riscv_pmu_sbi.c
> > > > +++ b/drivers/perf/riscv_pmu_sbi.c
> > > > @@ -693,6 +693,28 @@ static int pmu_sbi_setup_irqs(struct
> > > > riscv_pmu *pmu, struct platform_device *pde return 0;
> > > >  }
> > > >
> > > > +static ssize_t id_show(struct device *dev,
> > > > +                               struct device_attribute *attr,
> > > > char *buf) +{
> > > > +       int len;
> > > > +       struct riscv_pmu *pmu =
> > > > container_of(dev_get_drvdata(dev), struct riscv_pmu, pmu); +
> > > > +       len = sprintf(buf, "%s\n", pmu->pmuid);
> > > > +       if (len <= 0)
> > > > +               dev_err(dev, "invalid sprintf len: %d\n", len);
> > > > +
> > > > +       return len;
> > > > +}
> > > > +
> > > > +static DEVICE_ATTR(id, 0644, id_show, NULL);
> > > > +
> > > > +static struct attribute *pmu_sbi_attrs[] = {
> > > > +       &dev_attr_id.attr,
> > > > +       NULL
> > > > +};
> > > > +
> > > > +ATTRIBUTE_GROUPS(pmu_sbi);
> > > > +
> > > >  static int pmu_sbi_device_probe(struct platform_device *pdev)
> > > >  {
> > > >         struct riscv_pmu *pmu = NULL;
> > > > @@ -714,6 +736,14 @@ static int pmu_sbi_device_probe(struct
> > > > platform_device *pdev) if (pmu_sbi_get_ctrinfo(num_counters))
> > > >                 goto out_free;
> > > >
> > > > +       /* fill pmuid */
> > > > +       pmu->pmuid = kasprintf(GFP_KERNEL, "0x%lx,0x%lx,0x%lx",
> > > > +                              sbi_get_marchid(),
> > > > +                              sbi_get_mimpid(),
> > > > +                              sbi_get_mvendorid());
> > > > +       if (!pmu->pmuid)
> > > > +               goto out_free_pmuid;
> > > > +
> > > >         ret = pmu_sbi_setup_irqs(pmu, pdev);
> > > >         if (ret < 0) {
> > > >                 pr_info("Perf sampling/filtering is not
> > > > supported as sscof extension is not available\n"); @@ -739,8
> > > > +769,19 @@ static int pmu_sbi_device_probe(struct
> > > > platform_device *pdev) return ret; }
> > > >
> > > > +       ret = sysfs_create_group(&pdev->dev.kobj,
> > > > &pmu_sbi_group);
> > > > +       if (ret) {
> > > > +               dev_err(&pdev->dev, "sysfs creation failed\n");
> > > > +               return ret;
> > > > +       }
> > > > +
> > > > +       pdev->dev.groups = pmu_sbi_groups;
> > > > +       dev_set_drvdata(&pdev->dev, pmu);
> > > > +
> > > >         return 0;
> > > >
> > > > +out_free_pmuid:
> > > > +       kfree(pmu->pmuid);
> > > >  out_free:
> > > >         kfree(pmu);
> > > >         return ret;
> > > > diff --git a/include/linux/perf/riscv_pmu.h
> > > > b/include/linux/perf/riscv_pmu.h index
> > > > 46f9b6fe306e..cf3557b77fb8 100644 ---
> > > > a/include/linux/perf/riscv_pmu.h +++
> > > > b/include/linux/perf/riscv_pmu.h @@ -42,6 +42,7 @@ struct
> > > > cpu_hw_events { struct riscv_pmu {
> > > >         struct pmu      pmu;
> > > >         char            *name;
> > > > +       char            *pmuid;
> > > >
> > > >         irqreturn_t     (*handle_irq)(int irq_num, void *dev);
> > > >
> > > > --
> > > > 2.35.1
> > > >  
> >  
> 
> 


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