Re: [PATCH V3 10/20] RISC-V: smpboot: Add ACPI support in smp_setup()

[Andrew Jones]

On Fri, Mar 03, 2023 at 07:06:37PM +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@xxxxxxxxxxxxxxxx>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> ---
>  arch/riscv/kernel/smpboot.c | 72 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 71 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index 26214ddefaa4..27047322d3bb 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 +71,72 @@ 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;
> +	static bool found_boot_cpu;
> +	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;
> +
> +	if (BAD_MADT_ENTRY(processor, end))
> +		return -EINVAL;
> +
> +	acpi_table_print_madt_entry(&header->common);
> +
> +	hart = processor->hart_id;
> +	if (hart == INVALID_HARTID) {
> +		pr_warn("Invalid hartid\n");
> +		return 0;
> +	}
> +
> +	if (hart == cpuid_to_hartid_map(0)) {
> +		BUG_ON(found_boot_cpu);
> +		found_boot_cpu = true;
> +		early_map_cpu_to_node(0, NUMA_NO_NODE);

We should have kept

 static inline int acpi_numa_get_nid(unsigned int cpu) { return NUMA_NO_NODE; }

and only dropped the

 #ifdef CONFIG_ACPI_NUMA
 int acpi_numa_get_nid(unsigned int cpu);
 #else
 ...
 #endif

> +		return 0;
> +	}
> +
> +	if (cpu_count >= NR_CPUS) {
> +		pr_warn("NR_CPUS is too small for the number of ACPI tables.\n");
> +		return 0;
> +	}
> +
> +	cpuid_to_hartid_map(cpu_count) = hart;
> +	early_map_cpu_to_node(cpu_count, NUMA_NO_NODE);
> +	cpu_count++;
> +
> +	return 0;
> +}
> +
> +static void __init acpi_parse_and_init_cpus(void)
> +{
> +	int cpuid;
> +
> +	cpu_set_ops(0);
> +
> +	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 +185,10 @@ 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
>

Thanks,
drew