Re: [PATCH v2 06/18] ARM64 / ACPI: Parse MADT to map logical cpu to MPIDR and get cpu_possible/present_map

[Sudeep Holla]

On 04/08/14 16:28, Hanjun Guo wrote:
> MADT contains the information for MPIDR which is essential for
> SMP initialization, parse the GIC cpu interface structures to
> get the MPIDR value and map it to cpu_logical_map(), and add
> enabled cpu with valid MPIDR into cpu_possible_map and
> cpu_present_map.
>
> Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
> Signed-off-by: Tomasz Nowicki <tomasz.nowicki@xxxxxxxxxx>
> ---
>   arch/arm64/include/asm/acpi.h |    2 +
>   arch/arm64/kernel/acpi.c      |  129 ++++++++++++++++++++++++++++++++++++++++-
>   arch/arm64/kernel/smp.c       |   10 +++-
>   3 files changed, 138 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> index 6e04868..e877967 100644
> --- a/arch/arm64/include/asm/acpi.h
> +++ b/arch/arm64/include/asm/acpi.h
> @@ -64,6 +64,8 @@ static inline void arch_fix_phys_package_id(int num, u32 slot) { }
>   extern int (*acpi_suspend_lowlevel)(void);
>   #define acpi_wakeup_address 0
>
> +#define MAX_GIC_CPU_INTERFACE 65535
> +

Did you get this information from GIC specification ?

IIUC you are trying to represent max number of interrupt controller
entries MADT can possibly have. So, I had suggested to change the name
like MAX_MADT_INTERRUPT_CONTROLLER_ENTRIES so that it is not GIC specific.

>   #endif /* CONFIG_ACPI */
>
>   #endif /*_ASM_ACPI_H*/
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index 69a315d..9e07d99 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -22,6 +22,9 @@
>   #include <linux/bootmem.h>
>   #include <linux/smp.h>
>
> +#include <asm/smp_plat.h>
> +#include <asm/cputype.h>
> +
>   int acpi_noirq;			/* skip ACPI IRQ initialization */
>   int acpi_disabled;
>   EXPORT_SYMBOL(acpi_disabled);
> @@ -29,6 +32,8 @@ EXPORT_SYMBOL(acpi_disabled);
>   int acpi_pci_disabled;		/* skip ACPI PCI scan and IRQ initialization */
>   EXPORT_SYMBOL(acpi_pci_disabled);
>
> +static int enabled_cpus;	/* Processors (GICC) with enabled flag in MADT */
> +
>   /*
>    * __acpi_map_table() will be called before page_init(), so early_ioremap()
>    * or early_memremap() should be called here to for ACPI table mapping.
> @@ -49,6 +54,122 @@ void __init __acpi_unmap_table(char *map, unsigned long size)
>   	early_memunmap(map, size);
>   }
>
> +/**
> + * acpi_register_gic_cpu_interface - register a gic cpu interface and
> + * generates a logical cpu number
> + * @mpidr: CPU's hardware id to register, MPIDR represented in MADT
> + * @enabled: this cpu is enabled or not
> + *
> + * Returns the logical cpu number which maps to the gic cpu interface
> + */
> +static int acpi_register_gic_cpu_interface(u64 mpidr, u8 enabled)
> +{

IMO the function name gives me a wrong idea that you are registering
something with GIC. How about acpi_map_gic_cpu_interface ?

> +	int cpu;
> +
> +	if (mpidr == INVALID_HWID) {
> +		pr_info("Skip invalid cpu hardware ID\n");
> +		return -EINVAL;
> +	}
> +
> +	total_cpus++;
> +	if (!enabled)
> +		return -EINVAL;
> +
> +	if (enabled_cpus >=  NR_CPUS) {
> +		pr_warn("NR_CPUS limit of %d reached, Processor %d/0x%llx ignored.\n",
> +			NR_CPUS, total_cpus, mpidr);
> +		return -EINVAL;
> +	}
> +
> +	/* If it is the first CPU, no need to check duplicate MPIDRs */
> +	if (!enabled_cpus)
> +		goto skip_mpidr_check;
> +
> +	/*
> +	 * Duplicate MPIDRs are a recipe for disaster. Scan
> +	 * all initialized entries and check for
> +	 * duplicates. If any is found just ignore the CPU.
> +	 */
> +	for_each_present_cpu(cpu) {
> +		if (cpu_logical_map(cpu) == mpidr) {
> +			pr_err("Firmware bug, duplicate CPU MPIDR: 0x%llx in MADT\n",
> +			       mpidr);
> +			return -EINVAL;
> +		}
> +	}
> +
> +skip_mpidr_check:
> +	enabled_cpus++;
> +
> +	/* allocate a logical cpu id for the new comer */
> +	if (cpu_logical_map(0) == mpidr) {
> +		/*
> +		 * boot_cpu_init() already hold bit 0 in cpu_present_mask
> +		 * for BSP, no need to allocate again.
> +		 */
> +		cpu = 0;
> +	} else {
> +		cpu = cpumask_next_zero(-1, cpu_present_mask);
> +	}
> +
> +	/* map the logical cpu id to cpu MPIDR */
> +	cpu_logical_map(cpu) = mpidr;
> +
> +	set_cpu_possible(cpu, true);

IMO it better to keep all these updates to cpumasks contained in the
smp.c as I had mentioned before. I think you can refactor smp_init_cpus
to achieve that.

> +	set_cpu_present(cpu, true);

This is totally wrong ? What would you do if the cpu failed to
initialize ? I don't see that handled.

> +
> +	return cpu;
> +}
> +
> +static int __init
> +acpi_parse_gic_cpu_interface(struct acpi_subtable_header *header,
> +				const unsigned long end)
> +{
> +	struct acpi_madt_generic_interrupt *processor;
> +
> +	processor = (struct acpi_madt_generic_interrupt *)header;
> +
> +	if (BAD_MADT_ENTRY(processor, end))
> +		return -EINVAL;
> +
> +	acpi_table_print_madt_entry(header);
> +
> +	acpi_register_gic_cpu_interface(processor->arm_mpidr,
> +		processor->flags & ACPI_MADT_ENABLED);
> +
> +	return 0;
> +}
> +
> +/*
> + * Parse GIC cpu interface related entries in MADT
> + * returns 0 on success, < 0 on error
> + */
> +static int __init acpi_parse_madt_gic_cpu_interface_entries(void)
> +{
> +	int count;
> +
> +	/*
> +	 * do a partial walk of MADT to determine how many CPUs
> +	 * we have including disabled CPUs, and get information
> +	 * we need for SMP init
> +	 */
> +	count = acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT,
> +			acpi_parse_gic_cpu_interface, MAX_GIC_CPU_INTERFACE);
> +
> +	if (!count) {
> +		pr_err("No GIC CPU interface entries present\n");
> +		return -ENODEV;
> +	} else if (count < 0) {
> +		pr_err("Error parsing GIC CPU interface entry\n");
> +		return count;
> +	}
> +
> +	/* Make boot-up look pretty */
> +	pr_info("%d CPUs enabled, %d CPUs total\n", enabled_cpus, total_cpus);

Ideally just setup cpu_logical_map in acpi_parse_gic_cpu_interface and
setup cpumasks in smp_init_cpus.

> +
> +	return 0;
> +}
> +
>   static int __init acpi_parse_fadt(struct acpi_table_header *table)
>   {
>   	struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;
> @@ -99,8 +220,12 @@ int __init acpi_boot_init(void)
>   		return -ENODEV;
>
>   	err = acpi_table_parse(ACPI_SIG_FADT, acpi_parse_fadt);
> -	if (err)
> -		pr_err("Can't find FADT\n");
> +	if (err) {
> +		pr_err("Can't find FADT or error happened during parsing FADT\n");
> +		return err;
> +	}
> +
> +	err = acpi_parse_madt_gic_cpu_interface_entries();
>
>   	return err;
>   }
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 40f38f4..8f1d37c 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -36,6 +36,7 @@
>   #include <linux/completion.h>
>   #include <linux/of.h>
>   #include <linux/irq_work.h>
> +#include <linux/acpi.h>
>
>   #include <asm/atomic.h>
>   #include <asm/cacheflush.h>
> @@ -458,7 +459,14 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
>   		if (err)
>   			continue;
>
> -		set_cpu_present(cpu, true);
> +		/*
> +		 * In ACPI mode, cpu_present_map was initialised when
> +		 * MADT table was parsed which before this function
> +		 * is called.
> +		 */
> +		if (acpi_disabled)
> +			set_cpu_present(cpu, true);
> +

This is the right place to set the cpu present based on the return value
of cpu_prepare.

>   		max_cpus--;
>   	}
>   }

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