Subject: [PATCH 07/19] ARM64 / ACPI: Parse MADT to map logical cpu to MPIDR and get cpu_possible/present_map

From: [email-masked] (Hanjun Guo)
Date: Thu, 31 Jul 2014 16:14:10 +0800

On 2014-7-31 2:20, Sudeep Holla wrote:
> 
> 
> On 24/07/14 14:00, 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 <[email-masked]>
>> Signed-off-by: Tomasz Nowicki <[email-masked]>
>> ---
>>   arch/arm64/include/asm/acpi.h |    2 +
>>   arch/arm64/kernel/acpi.c      |  127 +++++++++++++++++++++++++++++++++++++++++
>>   arch/arm64/kernel/smp.c       |   10 +++-
>>   3 files changed, 138 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
>> index 67dac90..5ce85f8 100644
>> --- a/arch/arm64/include/asm/acpi.h
>> +++ b/arch/arm64/include/asm/acpi.h
>> @@ -50,6 +50,8 @@ static inline bool acpi_has_cpu_in_madt(void)
>>   extern int (*acpi_suspend_lowlevel)(void);
>>   #define acpi_wakeup_address 0
>>
>> +#define MAX_GIC_CPU_INTERFACE 65535
>> +
> 
> Can this me made something like MAX_MADT_INTERRUPT_CONTROLLER_ENTRIES ?

It is GIC CPU interface structure, I think we can keep the name as it
is or as ACPI_GIC_MAX_CPU_INTERFACE which modified in later patches.

> And assuming each entry to be at-least 4 or 8 bytes, it can be reduced.

Sorry, I didn't catch up with you here, can you explain it?

> 
>>   #endif /* CONFIG_ACPI */
>>
>>   #endif /*_ASM_ACPI_H*/
>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
>> index 374926f..801e268 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>
>> +
>>   /*
>>    * We never plan to use RSDT on arm/arm64 as its deprecated in spec but this
>>    * variable is still required by the ACPI core
>> @@ -42,6 +45,9 @@ int acpi_psci_present;
>>   /* 1 to indicate HVC must be used instead of SMC as the PSCI conduit */
>>   int acpi_psci_use_hvc;
>>
>> +/* Processors (GICC) with enabled flag in MADT */
>> +static int enabled_cpus;
>> +
>>   /*
>>    * __acpi_map_table() will be called before page_init(), so early_ioremap()
>>    * or early_memremap() should be called here to for ACPI table mapping.
>> @@ -62,6 +68,122 @@ void __init __acpi_unmap_table(char *map, unsigned long size)
>>       early_iounmap(map, size);
>>   }
>>
>> +/**
>> + * acpi_register_gic_cpu_interface - register a gic cpu interface and
>> + * generates a logic cpu number
>> + * @mpidr: CPU's hardware id to register, MPIDR represented in MADT
>> + * @enabled: this cpu is enabled or not
>> + *
>> + * Returns the logic cpu number which maps to the gic cpu interface
>> + */
>> +static int acpi_register_gic_cpu_interface(u64 mpidr, u8 enabled)
> 
> Honestly this function doesn't deal anything with GIC cpu interface.

Yes, but every GIC cpu interface structure represents a CPU in the
system, it is about the SMP init.

> 
>> +{
>> +    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 logic 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 allocte again.
>> +         */
>> +        cpu = 0;
>> +    } else {
>> +        cpu = cpumask_next_zero(-1, cpu_present_mask);
>> +    }
>> +
>> +    /* map the logic cpu id to cpu MPIDR */
>> +    cpu_logical_map(cpu) = mpidr;
>> +
>> +    set_cpu_possible(cpu, true);
>> +    set_cpu_present(cpu, true);
>> +
> 
> I need to think more about this function and will comment later but I
> think these cpumasks should be set only if SMP and probably belong to smp.c

No, I don't think so, it is because of the CPU hot add.

Considering a CPU will be added at run-time (you may fine out this function
without __init), it will go through the ACPI routing and call this function
to map its MPIDR to cpu logical num and then call cpu_up() to online it,
so if you move these cpumasks to __init functions in smp.c, new CPUs added
at run-time will never be set for there possible and present mask.

> 
>> +    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->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);
>> +
>> +    return 0;
>> +}
>> +
>>   static int __init acpi_parse_fadt(struct acpi_table_header *table)
>>   {
>>       struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;
>> @@ -122,6 +244,11 @@ int __init acpi_boot_init(void)
>>       if (err)
>>           pr_err("Can't find FADT\n");
>>
>> +    /* Get the boot CPU's MPIDR before MADT parsing */
>> +    cpu_logical_map(0) = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
>> +
> 
> As Mark suggested better to move this prior to ACPI changes.

I will.

> 
>> +    err = acpi_parse_madt_gic_cpu_interface_entries();
>> +
> 
> OK, so now you ignore if there was any FADT error if MADT is
> successfully parsed ?

My original intention is that we can continue the MADT table
parsing even if we meet some error when parsing FADT, just
as x86 did. But now ACPI is disabled when FADT version is not
correct, so I think we need check here as you said.

> 
>>       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 what I said above, it belongs here and we need to see how we do
> that. I will give it a thought.

Please refer to the comments above.

Thanks
Hanjun