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

Conor Dooley
2022-07-19T14:38:45Z

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@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@arm.com>
>> Reviewed-by: Gavin Shan <gshan@redhat.com>
>> Signed-off-by: Sudeep Holla <sudeep.holla@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@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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