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

[Conor Dooley]

On 19/07/2022 15:22, Geert Uytterhoeven wrote:
> Hi Sudeep,

Hey Geert,

 
> On Mon, Jul 4, 2022 at 12:19 PM Sudeep Holla <sudeep.holla@xxxxxxx> 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@xxxxxxx>
> > Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>
> > Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
>
> 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).

This should be fixed by Sudeeps most recent patchset, at least
it was when I tested it!
https://lore.kernel.org/all/20220713133344.1201247-1-sudeep.holla@xxxxxxx/

> -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@xxxxxxxxxxxxxx
>
> 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
>
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