[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 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).

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@arm.com/

> -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
> 
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