On Tue, 04 Apr 2023 11:20:22 PDT (-0700), [email protected] wrote:
> RINTC structures in the MADT provide mapping between the hartid
> and the CPU. This is required many times even at run time like
> cpuinfo. So, instead of parsing the ACPI table every time, cache
> the RINTC structures and provide a function to get the correct
> RINTC structure for a given cpu.
>
> Signed-off-by: Sunil V L <[email protected]>
> Acked-by: Rafael J. Wysocki <[email protected]>
> ---
> arch/riscv/include/asm/acpi.h | 2 ++
> arch/riscv/kernel/acpi.c | 60 +++++++++++++++++++++++++++++++++++
> 2 files changed, 62 insertions(+)
>
> diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
> index 9be52b6ffae1..1606dce8992e 100644
> --- a/arch/riscv/include/asm/acpi.h
> +++ b/arch/riscv/include/asm/acpi.h
> @@ -59,6 +59,8 @@ static inline bool acpi_has_cpu_in_madt(void)
>
> static inline void arch_fix_phys_package_id(int num, u32 slot) { }
>
> +struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu);
> +u32 get_acpi_id_for_cpu(int cpu);
> #endif /* CONFIG_ACPI */
>
> #endif /*_ASM_ACPI_H*/
> diff --git a/arch/riscv/kernel/acpi.c b/arch/riscv/kernel/acpi.c
> index 81d448c41714..40ab55309c70 100644
> --- a/arch/riscv/kernel/acpi.c
> +++ b/arch/riscv/kernel/acpi.c
> @@ -24,6 +24,66 @@ EXPORT_SYMBOL(acpi_disabled);
> int acpi_pci_disabled = 1; /* skip ACPI PCI scan and IRQ initialization */
> EXPORT_SYMBOL(acpi_pci_disabled);
>
> +static struct acpi_madt_rintc cpu_madt_rintc[NR_CPUS];
> +
> +static int acpi_parse_madt_rintc(union acpi_subtable_headers *header, const unsigned long end)
> +{
> + struct acpi_madt_rintc *rintc = (struct acpi_madt_rintc *)header;
> + int cpuid;
> +
> + if (!(rintc->flags & ACPI_MADT_ENABLED))
> + return 0;
> +
> + cpuid = riscv_hartid_to_cpuid(rintc->hart_id);
Unless I'm missing something, this races with CPUs coming online. Maybe
that's a rare enough case we don't care, but I think we'd also just have
simpler logic if we fixed it...
> + /*
> + * When CONFIG_SMP is disabled, mapping won't be created for
> + * all cpus.
> + * CPUs more than NR_CPUS, will be ignored.
> + */
> + if (cpuid >= 0 && cpuid < NR_CPUS)
> + cpu_madt_rintc[cpuid] = *rintc;
> +
> + return 0;
> +}
> +
> +static int acpi_init_rintc_array(void)
> +{
> + if (acpi_table_parse_madt(ACPI_MADT_TYPE_RINTC, acpi_parse_madt_rintc, 0) > 0)
> + return 0;
> +
> + return -ENODEV;
> +}
> +
> +/*
> + * Instead of parsing (and freeing) the ACPI table, cache
> + * the RINTC structures since they are frequently used
> + * like in cpuinfo.
> + */
> +struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu)
> +{
> + static bool rintc_init_done;
... basically just get rid of this global variable, and instead have a
if (!&cpu_madt_rintc[cpu])
... parse ...
return &cpu_madt_rintc[cpu];
that'd probably let us get rid of a handful of these helpers too, as now
it's just a call to the parsing bits.
> +
> + if (!rintc_init_done) {
> + if (acpi_init_rintc_array()) {
> + pr_err("No valid RINTC entries exist\n");
> + return NULL;
> + }
> +
> + rintc_init_done = true;
> + }
> +
> + return &cpu_madt_rintc[cpu];
> +}
> +
> +u32 get_acpi_id_for_cpu(int cpu)
> +{
> + struct acpi_madt_rintc *rintc = acpi_cpu_get_madt_rintc(cpu);
> +
> + BUG_ON(!rintc);
We should have some better error reporting here. It looks like all the
callerss of get_acpi_id_for_cpu() are tolerant of a nonsense ID being
returned, so maybe we just pr_warn() something users can understand and
then return -1 or something?
> +
> + return rintc->uid;
> +}
> +
> /*
> * __acpi_map_table() will be called before paging_init(), so early_ioremap()
> * or early_memremap() should be called here to for ACPI table mapping.