Re: [PATCH v4 11/18] ARM64 / ACPI: Parse MADT for SMP initialization

[Olof Johansson <olof@lixom.net>]

On Fri, Sep 12, 2014 at 10:00:09PM +0800, 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.
> 
> ACPI 5.1 only has two explicit methods to boot up SMP, PSCI and
> Parking protocol, but the Parking protocol is only specified for
> ARMv7 now, so make PSCI as the only way for the SMP boot protocol
> before some updates for the ACPI spec or the Parking protocol spec.
> 
> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
> Signed-off-by: Tomasz Nowicki <tomasz.nowicki@linaro.org>
> ---
>  arch/arm64/include/asm/acpi.h    |    2 +
>  arch/arm64/include/asm/cpu_ops.h |    1 +
>  arch/arm64/include/asm/smp.h     |    5 +-
>  arch/arm64/kernel/acpi.c         |  147 +++++++++++++++++++++++++++++++++++++-
>  arch/arm64/kernel/cpu_ops.c      |    4 +-
>  arch/arm64/kernel/setup.c        |    8 ++-
>  arch/arm64/kernel/smp.c          |    2 +-
>  7 files changed, 160 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> index ecba671..da8f74a 100644
> --- a/arch/arm64/include/asm/acpi.h
> +++ b/arch/arm64/include/asm/acpi.h
> @@ -51,11 +51,13 @@ static inline bool acpi_has_cpu_in_madt(void)
>  }
>  
>  static inline void arch_fix_phys_package_id(int num, u32 slot) { }
> +void __init acpi_smp_init_cpus(void);
>  
>  #else
>  
>  static inline bool acpi_psci_present(void) { return false; }
>  static inline bool acpi_psci_use_hvc(void) { return false; }
> +static inline void acpi_smp_init_cpus(void) { }
>  
>  #endif /* CONFIG_ACPI */
>  
> diff --git a/arch/arm64/include/asm/cpu_ops.h b/arch/arm64/include/asm/cpu_ops.h
> index d7b4b38..d149580 100644
> --- a/arch/arm64/include/asm/cpu_ops.h
> +++ b/arch/arm64/include/asm/cpu_ops.h
> @@ -61,6 +61,7 @@ struct cpu_operations {
>  };
>  
>  extern const struct cpu_operations *cpu_ops[NR_CPUS];
> +const struct cpu_operations *cpu_get_ops(const char *name);
>  extern int __init cpu_read_ops(struct device_node *dn, int cpu);
>  extern void __init cpu_read_bootcpu_ops(void);
>  
> diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
> index a498f2c..c877adc 100644
> --- a/arch/arm64/include/asm/smp.h
> +++ b/arch/arm64/include/asm/smp.h
> @@ -39,9 +39,10 @@ extern void show_ipi_list(struct seq_file *p, int prec);
>  extern void handle_IPI(int ipinr, struct pt_regs *regs);
>  
>  /*
> - * Setup the set of possible CPUs (via set_cpu_possible)
> + * Discover the set of possible CPUs and determine their
> + * SMP operations.
>   */
> -extern void smp_init_cpus(void);
> +extern void of_smp_init_cpus(void);
>  
>  /*
>   * Provide a function to raise an IPI cross call on CPUs in callmap.
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index 9e1ae37..644b8b8 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -24,6 +24,10 @@
>  #include <linux/bootmem.h>
>  #include <linux/smp.h>
>  
> +#include <asm/smp_plat.h>
> +#include <asm/cputype.h>
> +#include <asm/cpu_ops.h>
> +
>  int acpi_noirq;			/* skip ACPI IRQ initialization */
>  int acpi_disabled;
>  EXPORT_SYMBOL(acpi_disabled);
> @@ -31,6 +35,8 @@ 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.
> @@ -51,6 +57,131 @@ void __init __acpi_unmap_table(char *map, unsigned long size)
>  	early_memunmap(map, size);
>  }
>  
> +/**
> + * acpi_map_gic_cpu_interface - generates a logical cpu number
> + * and map to MPIDR represented by GICC structure
> + * @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 MPIDR
> + */
> +static int acpi_map_gic_cpu_interface(u64 mpidr, u8 enabled)
> +{
> +	int cpu;
> +
> +	if (mpidr == INVALID_HWID) {
> +		pr_info("Skip invalid cpu hardware ID\n");

This message, when showing up in dmesg, will probably mostly just make
someone scratch their head. Something slightly more descriptive would
be a good idea.

> +		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;
> +	}
> +
> +	/* No need to check duplicate MPIDRs for the first CPU */
> +	if (enabled_cpus) {
> +		/*
> +		 * Duplicate MPIDRs are a recipe for disaster. Scan
> +		 * all initialized entries and check for
> +		 * duplicates. If any is found just ignore the CPU.
> +		 */

But is it this entry or the other one that should be ignored? Is
this expected to be something that firmware vendors get wrong all the
time? Would it be better to abort SMP alltogether?

> +		for_each_possible_cpu(cpu) {
> +			if (cpu_logical_map(cpu) == mpidr) {
> +				pr_err("Firmware bug, duplicate CPU MPIDR: 0x%llx in MADT\n",
> +				mpidr);

Misindented.

> +				return -EINVAL;
> +			}
> +		}
> +		
> +		/* allocate a logical cpu id for the new comer */
> +		cpu = cpumask_next_zero(-1, cpu_possible_mask);
> +	} else {
> +		/* First GICC entry must be BSP as ACPI spec said */

"spec said", would be nice to have a chapter/section reference.

> +		if  (cpu_logical_map(0) != mpidr) {
> +			pr_err("First GICC entry with MPIDR 0x%llx is not BSP\n",
> +			       mpidr);

Same thing here about usefulness of error message. What is a user to do with this?

> +			return -EINVAL;
> +		}
> +
> +		/*
> +		 * boot_cpu_init() already hold bit 0 in cpu_present_mask
> +		 * for BSP, no need to allocate again.
> +		 */
> +		cpu = 0;
> +	}
> +
> +	/* CPU 0 was already initialized */
> +	if (cpu) {
> +		cpu_ops[cpu] = cpu_get_ops(acpi_psci_present() ? "psci" : NULL);
> +		if (!cpu_ops[cpu])
> +			return -EINVAL;
> +
> +		if (cpu_ops[cpu]->cpu_init(NULL, cpu))
> +			return -EOPNOTSUPP;
> +
> +		/* map the logical cpu id to cpu MPIDR */
> +		cpu_logical_map(cpu) = mpidr;
> +
> +		set_cpu_possible(cpu, true);
> +	} else {
> +		/* get cpu0's ops, no need to return if ops is null */
> +		cpu_ops[0] = cpu_get_ops(acpi_psci_present() ? "psci" : NULL);
> +	}
> +
> +	enabled_cpus++;
> +	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_map_gic_cpu_interface(processor->arm_mpidr & MPIDR_HWID_BITMASK,
> +		processor->flags & ACPI_MADT_ENABLED);
> +
> +	return 0;
> +}
> +
> +/* Parse GIC cpu interface entries in MADT for SMP init */
> +void __init acpi_smp_init_cpus(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, 0);
> +
> +	if (!count) {
> +		pr_err("No GIC CPU interface entries present\n");
> +		return;
> +	} else if (count < 0) {
> +		pr_err("Error parsing GIC CPU interface entry\n");
> +		return;
> +	}
> +
> +	/* Make boot-up look pretty */
> +	pr_info("%d CPUs enabled, %d CPUs total\n", enabled_cpus, total_cpus);
> +}
> +
>  static int __init acpi_parse_fadt(struct acpi_table_header *table)
>  {
>  	struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;
> @@ -62,8 +193,20 @@ static int __init acpi_parse_fadt(struct acpi_table_header *table)
>  	 * to get arm boot flags, or we will disable ACPI.
>  	 */
>  	if (table->revision > 5 ||
> -	    (table->revision == 5 && fadt->minor_revision >= 1))
> -		return 0;
> +	    (table->revision == 5 && fadt->minor_revision >= 1)) {
> +		/*
> +		 * ACPI 5.1 only has two explicit methods to boot up SMP,
> +		 * PSCI and Parking protocol, but the Parking protocol is
> +		 * only specified for ARMv7 now, so make PSCI as the only
> +		 * way for the SMP boot protocol before some updates for
> +		 * the ACPI spec or the Parking protocol spec.
> +		 */
> +		if (acpi_psci_present())
> +			return 0;
> +
> +		pr_warn("has no PSCI support, will not bring up secondary CPUs\n");

s/has//

> +		return -EOPNOTSUPP;
> +	}
>  
>  	pr_warn("Unsupported FADT revision %d.%d, should be 5.1+, will disable ACPI\n",
>  		table->revision, fadt->minor_revision);
> diff --git a/arch/arm64/kernel/cpu_ops.c b/arch/arm64/kernel/cpu_ops.c
> index cce9524..1a04deb 100644
> --- a/arch/arm64/kernel/cpu_ops.c
> +++ b/arch/arm64/kernel/cpu_ops.c
> @@ -27,7 +27,7 @@ extern const struct cpu_operations cpu_psci_ops;
>  
>  const struct cpu_operations *cpu_ops[NR_CPUS];
>  
> -static const struct cpu_operations *supported_cpu_ops[] __initconst = {
> +static const struct cpu_operations *supported_cpu_ops[] = {
>  #ifdef CONFIG_SMP
>  	&smp_spin_table_ops,
>  #endif
> @@ -35,7 +35,7 @@ static const struct cpu_operations *supported_cpu_ops[] __initconst = {
>  	NULL,
>  };
>  
> -static const struct cpu_operations * __init cpu_get_ops(const char *name)
> +const struct cpu_operations *cpu_get_ops(const char *name)
>  {
>  	const struct cpu_operations **ops = supported_cpu_ops;
>  
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 7ba20d4..281fa34 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -60,6 +60,7 @@
>  #include <asm/memblock.h>
>  #include <asm/psci.h>
>  #include <asm/efi.h>
> +#include <asm/acpi.h>
>  
>  unsigned int processor_id;
>  EXPORT_SYMBOL(processor_id);
> @@ -401,13 +402,16 @@ void __init setup_arch(char **cmdline_p)
>  	if (acpi_disabled) {
>  		unflatten_device_tree();
>  		psci_dt_init();
> +		cpu_read_bootcpu_ops();
> +#ifdef CONFIG_SMP
> +		of_smp_init_cpus();
> +#endif

Please create a !SMP stub so you can do without the ifdef here, just
like you did for the ACPI case.

>  	} else {
>  		psci_acpi_init();
> +		acpi_smp_init_cpus();
>  	}
>  
> -	cpu_read_bootcpu_ops();
>  #ifdef CONFIG_SMP
> -	smp_init_cpus();
>  	smp_build_mpidr_hash();
>  #endif
>  
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 4743397..4e390ac 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -321,7 +321,7 @@ void __init smp_prepare_boot_cpu(void)
>   * cpu logical map array containing MPIDR values related to logical
>   * cpus. Assumes that cpu_logical_map(0) has already been initialized.
>   */
> -void __init smp_init_cpus(void)
> +void __init of_smp_init_cpus(void)
>  {
>  	struct device_node *dn = NULL;
>  	unsigned int i, cpu = 1;
> -- 
> 1.7.9.5
> 


-Olof