Re: [PATCH V2 10/21] RISC-V: smpboot: Add ACPI support in smp_setup()

Sunil V L
2023-02-24T16:50:43Z

On Mon, Feb 20, 2023 at 06:08:43PM +0100, Andrew Jones wrote:
> On Thu, Feb 16, 2023 at 11:50:32PM +0530, Sunil V L wrote:
> > Enable SMP boot on ACPI based platforms by using the RINTC
> > structures in the MADT table.
> >
> > Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > ---
> > arch/riscv/include/asm/acpi.h | 7 ++++
> > arch/riscv/kernel/smpboot.c | 70 ++++++++++++++++++++++++++++++++++-
> > 2 files changed, 76 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
> > index 7bc49f65c86b..3c3a8ac3b37a 100644
> > --- a/arch/riscv/include/asm/acpi.h
> > +++ b/arch/riscv/include/asm/acpi.h
> > @@ -60,6 +60,13 @@ static inline void arch_fix_phys_package_id(int num, u32 slot) { }
> >
> > int acpi_get_riscv_isa(struct acpi_table_header *table,
> > unsigned int cpu, const char **isa);
> > +
> > +#ifdef CONFIG_ACPI_NUMA
> > +int acpi_numa_get_nid(unsigned int cpu);
> > +#else
> > +static inline int acpi_numa_get_nid(unsigned int cpu) { return NUMA_NO_NODE; }
> > +#endif /* CONFIG_ACPI_NUMA */
>
> The #ifdef stuff seems premature since we're not providing an
> implementation for acpi_numa_get_nid() or selecting ACPI_NUMA, but OK.
>
Yes, will remove it. We can add as part NUMA enablement.

> > +
> > #else
> > static inline int acpi_get_riscv_isa(struct acpi_table_header *table,
> > unsigned int cpu, const char **isa)
> > diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> > index 26214ddefaa4..77630f8ed12b 100644
> > --- a/arch/riscv/kernel/smpboot.c
> > +++ b/arch/riscv/kernel/smpboot.c
> > @@ -8,6 +8,7 @@
> > * Copyright (C) 2017 SiFive
> > */
> >
> > +#include <linux/acpi.h>
> > #include <linux/arch_topology.h>
> > #include <linux/module.h>
> > #include <linux/init.h>
> > @@ -70,6 +71,70 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
> > }
> > }
> >
> > +#ifdef CONFIG_ACPI
> > +static unsigned int cpu_count = 1;
> > +
> > +static int __init acpi_parse_rintc(union acpi_subtable_headers *header, const unsigned long end)
> > +{
> > + unsigned long hart;
> > + bool found_boot_cpu = false;
>
> I guess found_boot_cpu should be static?
>
Good catch!. Thanks!

> > + struct acpi_madt_rintc *processor = (struct acpi_madt_rintc *)header;
> > +
> > + /*
> > + * Each RINTC structure in MADT will have a flag. If ACPI_MADT_ENABLED
> > + * bit in the flag is not enabled, it means OS should not try to enable
> > + * the cpu to which RINTC belongs.
> > + */
> > + if (!(processor->flags & ACPI_MADT_ENABLED))
> > + return 0;
> > +
> > + hart = processor->hart_id;
> > + if (hart < 0)
> > + return 0;
>
> A valid hart ID is anything up to INVALID_HARTID, right? Shouldn't we only
> be checking for INVALID_HARTID here? And what does it mean to have an
> invalid hart ID here? It's not an issue to error/warn about?
>
Yes, will check for INVALID_HARTID (though I am not really sure how it
can be invalid). Will add a warning.

> > + if (hart == cpuid_to_hartid_map(0)) {
> > + BUG_ON(found_boot_cpu);
>
> Do we really want to BUG due to bad, but potentially bootable ACPI tables?
> I'd BUG for things that can only happen when we break the code, but broken
> ACPI tables might be something we want to complain loudly about and then
> attempt to limp along.
>
Okay. I used same logic as in DT. It may be better to use BUG instead of
debugging weird symptoms later, right?

> > + found_boot_cpu = true;
> > + early_map_cpu_to_node(0, acpi_numa_get_nid(cpu_count));
> > + return 0;
> > + }
> > +
> > + if (cpu_count >= NR_CPUS) {
> > + pr_warn("Invalid cpuid [%d] for hartid [%lu]\n",
> > + cpu_count, hart);
>
> cpuid isn't invalid, NR_CPUS is too small for the number of ACPI tables.
>
Okay.

> > + return 0;
> > + }
> > +
> > + cpuid_to_hartid_map(cpu_count) = hart;
> > + early_map_cpu_to_node(cpu_count, acpi_numa_get_nid(cpu_count));
> > + cpu_count++;
> > +
> > + return 0;
> > +}
> > +
> > +static void __init acpi_parse_and_init_cpus(void)
> > +{
> > + int cpuid;
> > +
> > + cpu_set_ops(0);
> > +
> > + /*
> > + * do a walk of MADT to determine how many CPUs
> > + * we have including disabled CPUs, and get information
> > + * we need for SMP init.
> > + */
>
> I know this comment comes verbatim from arm64, but not only does it
> have grammar issues, I'm not sure it's accurate. Where is the count
> of disabled CPUs for arm64 or riscv?
>
MADT will have multiple RINTC structures. Each RINTC structure will have
a flag to indicate whether enabled or disabled. So, we need to walk the
MADT to get all CPUs present. But I think this comment is not required
since comments are added in the parser function.

> > + acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC, acpi_parse_rintc, 0);
> > +
> > + for (cpuid = 1; cpuid < nr_cpu_ids; cpuid++) {
> > + if (cpuid_to_hartid_map(cpuid) != INVALID_HARTID) {
> > + cpu_set_ops(cpuid);
> > + set_cpu_possible(cpuid, true);
> > + }
> > + }
> > +}
> > +#else
> > +#define acpi_parse_and_init_cpus(...) do { } while (0)
> > +#endif
> > +
> > static void __init of_parse_and_init_cpus(void)
> > {
> > struct device_node *dn;
> > @@ -118,7 +183,10 @@ static void __init of_parse_and_init_cpus(void)
> >
> > void __init setup_smp(void)
> > {
> > - of_parse_and_init_cpus();
> > + if (acpi_disabled)
> > + of_parse_and_init_cpus();
> > + else
> > + acpi_parse_and_init_cpus();
> > }
> >
> > static int start_secondary_cpu(int cpu, struct task_struct *tidle)
> > --
> > 2.34.1
> >
>
> Do we not want to add an entry to acpi_table_print_madt_entry() for RINTC?
>
Yes. Will add a patch for this to help debugging.

Thanks,
Sunil