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

Geert Uytterhoeven
2022-07-19T14:23:37Z

Hi Sudeep,

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).
-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