[PATCH v6 09/21] arch_topology: Add support to parse and detect cache attributes

[Geert Uytterhoeven]

Hi Sudeep,

On Mon, Jul 4, 2022 at 12:19 PM Sudeep Holla <sudeep.holla at arm.com> wrote:
> Currently ACPI populates just the minimum information about the last
> level cache from PPTT in order to feed the same to build sched_domains.
> Similar support for DT platforms is not present.
>
> In order to enable the same, the entire cache hierarchy information can
> be built as part of CPU topoplogy parsing both on ACPI and DT platforms.
>
> Note that this change builds the cacheinfo early even on ACPI systems,
> but the current mechanism of building llc_sibling mask remains unchanged.
>
> Tested-by: Ionela Voinescu <ionela.voinescu at arm.com>
> Reviewed-by: Gavin Shan <gshan at redhat.com>
> Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>

Thanks for your patch!

> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -7,6 +7,7 @@
>   */
>
>  #include <linux/acpi.h>
> +#include <linux/cacheinfo.h>
>  #include <linux/cpu.h>
>  #include <linux/cpufreq.h>
>  #include <linux/device.h>
> @@ -780,15 +781,28 @@ __weak int __init parse_acpi_topology(void)
>  #if defined(CONFIG_ARM64) || defined(CONFIG_RISCV)
>  void __init init_cpu_topology(void)
>  {
> +       int ret, cpu;
> +
>         reset_cpu_topology();
> +       ret = parse_acpi_topology();
> +       if (!ret)
> +               ret = of_have_populated_dt() && parse_dt_topology();
>
> -       /*
> -        * Discard anything that was parsed if we hit an error so we
> -        * don't use partial information.
> -        */
> -       if (parse_acpi_topology())
> -               reset_cpu_topology();
> -       else if (of_have_populated_dt() && parse_dt_topology())
> +       if (ret) {
> +               /*
> +                * Discard anything that was parsed if we hit an error so we
> +                * don't use partial information.
> +                */
>                 reset_cpu_topology();
> +               return;
> +       }
> +
> +       for_each_possible_cpu(cpu) {
> +               ret = detect_cache_attributes(cpu);
> +               if (ret) {
> +                       pr_info("Early cacheinfo failed, ret = %d\n", ret);

This is triggered

    Early cacheinfo failed, ret = -12

on all my RV64 platforms (K210, PolarFire, StarLight).
-12 = -ENOMEM.

The boot continues regardless, and the K210 even has enough spare
RAM after boot to run "ls", unlike two weeks ago ;-)

> +                       break;
> +               }
> +       }
>  }

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds