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Re: [Xen-devel] [PATCH 6/7] xen/arm: Dissociate logical and hardware CPU ID



t gOn Fri, 2013-08-30 at 14:30 +0100, Julien Grall wrote:
> Introduce cpu_logical_map to associate a logical CPU ID to an hardware CPU ID.
> This map will be filled during Xen boot via the device tree. Each CPU node
> contains a "reg" property which contains the hardware ID (ie MPIDR[0:23]).
> 
> Also move /cpus parsing later so we can use the dt_* API.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>  xen/arch/arm/setup.c            |  109 
> ++++++++++++++++++++++++++++++++++++++-
>  xen/arch/arm/smpboot.c          |    4 ++
>  xen/common/device_tree.c        |   48 -----------------
>  xen/include/asm-arm/processor.h |    4 ++
>  4 files changed, 116 insertions(+), 49 deletions(-)
> 
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 137a65e..fabad91 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -496,6 +496,111 @@ void __init setup_cache(void)
>      cacheline_bytes = 1U << (4 + (ccsid & 0x7));
>  }
>  
> +/* Parse the device tree and build the logical map array containing
> + * MPIDR values related to logical cpus
> + * Code base on Linux arch/arm/kernel/devtree.c
> + */
> +static void __init init_cpus_maps(void)
> +{
> +    register_t mpidr;
> +    struct dt_device_node *cpus = dt_find_node_by_path("/cpus");
> +    struct dt_device_node *cpu;
> +    unsigned int i, j;
> +    unsigned int cpuidx = 1;
> +    u32 tmp_map[NR_CPUS] = { [0 ... NR_CPUS - 1] = MPIDR_INVALID };

This is potentially a fair bit of data on the stack? If yes then it
could be static init data?

> +    bool_t bootcpu_valid = 0;
> +
> +    mpidr = READ_SYSREG(MPIDR_EL1) & MPIDR_HWID_MASK;

boot_cpu_mpidr would have saved me wondering why the current CPU was so
special.

> +
> +    if ( !cpus )
> +    {
> +        printk(XENLOG_WARNING "WARNING: Can't find /cpus in the device 
> tree.\n"
> +               "Using only 1 CPU\n");
> +        return;
> +    }
> +
> +    for_each_child_node( cpus, cpu )
> +    {
> +        u32 hwid;
> +
> +        if ( !dt_device_type_is_equal(cpu, "cpu") )
> +            continue;
> +
> +        if ( !dt_property_read_u32(cpu, "reg", &hwid) )
> +        {
> +            printk(XENLOG_WARNING "cpu node `%s`: missing reg property\n",
> +                   dt_node_full_name(cpu));
> +            continue;
> +        }
> +
> +        /*
> +         * 8 MSBs must be set to 0 in the DT since the reg property
> +         * defines the MPIDR[23:0]
> +         */
> +        if ( hwid & ~MPIDR_HWID_MASK )
> +        {
> +            printk(XENLOG_WARNING "cpu node `%s`: invalid hwid value 
> (0x%x)\n",
> +                   dt_node_full_name(cpu), hwid);
> +            continue;
> +        }
> +
> +        /*
> +         * Duplicate MPIDRs are a recipe for disaster. Scan all initialized
> +         * entries and check for duplicates. If any found just skip the node.
> +         * temp values values are initialized to MPIDR_INVALID to avoid
> +         * matching valid MPIDR[23:0] values.
> +         */
> +        for ( j = 0; j < cpuidx; j++ )
> +        {
> +            if ( tmp_map[j] == hwid )
> +            {
> +                printk(XENLOG_WARNING "cpu node `%s`: duplicate /cpu reg 
> properties in the DT\n",
> +                       dt_node_full_name(cpu));
> +                continue;
> +            }
> +        }
> +
> +        /*
> +         * Build a stashed array of MPIDR values. Numbering scheme requires
> +         * that if detected the boot CPU must be assigned logical id 0. Other
> +         * CPUs get sequential indexes starting from 1. If a CPU node
> +         * with a reg property matching the boot CPU MPIDR is detected,
> +         * this is recorded and so that the logical map build from DT is
> +         * validated and can be used to set the map.
> +         */
> +        if ( hwid == mpidr )
> +        {
> +            i = 0;
> +            bootcpu_valid = 1;
> +        }
> +        else
> +            i = cpuidx++;
> +
> +        if ( cpuidx > NR_CPUS )
> +        {
> +            printk(XENLOG_WARNING "DT /cpu %u node greater than max cores 
> %u, capping them\n",
> +                   cpuidx, NR_CPUS);
> +            cpuidx = NR_CPUS;
> +            break;
> +        }
> +
> +        tmp_map[i] = hwid;
> +    }
> +
> +    if ( !bootcpu_valid )
> +    {
> +        printk(XENLOG_WARNING "DT missing boot CPU MPIDR[23:0]\n"
> +               "Using only 1 CPU\n");
> +        return;
> +    }
> +
> +    for ( i = 0; i < cpuidx; i++ )
> +    {
> +        cpumask_set_cpu(i, &cpu_possible_map);
> +        cpu_logical_map(i) = tmp_map[i];

For i == 0 this happens in smp_clear_cpu_maps too. You may as well start
from 1.

> +    }
> +}
> +
>  /* C entry point for boot CPU */
>  void __init start_xen(unsigned long boot_phys_offset,
>                        unsigned long fdt_paddr,
> @@ -515,7 +620,6 @@ void __init start_xen(unsigned long boot_phys_offset,
>          + (fdt_paddr & ((1 << SECOND_SHIFT) - 1));
>      fdt_size = device_tree_early_init(device_tree_flattened);
>  
> -    cpus = smp_get_max_cpus();
>      cmdline_parse(device_tree_bootargs(device_tree_flattened));
>  
>      setup_pagetables(boot_phys_offset, get_xen_paddr());
> @@ -528,6 +632,9 @@ void __init start_xen(unsigned long boot_phys_offset,
>      dt_uart_init();
>      console_init_preirq();
>  
> +    init_cpus_maps();
> +    cpus = smp_get_max_cpus();

It seems like anything which was previously using this should by now be
using some sort of for_each_foo() helper over the apropriate bitmasks?

> +
>      system_state = SYS_STATE_boot;
>  
>      processor_id();
> diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
> index b6aea63..c0d25de 100644
> --- a/xen/arch/arm/smpboot.c
> +++ b/xen/arch/arm/smpboot.c
> @@ -39,6 +39,9 @@ EXPORT_SYMBOL(cpu_possible_map);
>  
>  struct cpuinfo_arm cpu_data[NR_CPUS];
>  
> +/* CPU logical map: map xen cpuid to an MPIDR */
> +u32 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = MPIDR_INVALID };
> +
>  /* Fake one node for now. See also include/asm-arm/numa.h */
>  nodemask_t __read_mostly node_online_map = { { [0] = 1UL } };
>  
> @@ -82,6 +85,7 @@ smp_clear_cpu_maps (void)
>      cpumask_clear(&cpu_online_map);
>      cpumask_set_cpu(0, &cpu_online_map);
>      cpumask_set_cpu(0, &cpu_possible_map);
> +    cpu_logical_map(0) = READ_SYSREG(MPIDR_EL1) & MPIDR_HWID_MASK;
>  }
>  
>  int __init
> diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> index 5620b23..cc519af 100644
> --- a/xen/common/device_tree.c
> +++ b/xen/common/device_tree.c
> @@ -118,18 +118,6 @@ static bool_t __init device_tree_node_matches(const void 
> *fdt, int node,
>          && (name[match_len] == '@' || name[match_len] == '\0');
>  }
>  
> -static bool_t __init device_tree_type_matches(const void *fdt, int node,
> -                                       const char *match)
> -{
> -    const void *prop;
> -
> -    prop = fdt_getprop(fdt, node, "device_type", NULL);
> -    if ( prop == NULL )
> -        return 0;
> -
> -    return !dt_node_cmp(prop, match);
> -}
> -
>  static bool_t __init device_tree_node_compatible(const void *fdt, int node,
>                                                   const char *match)
>  {
> @@ -348,40 +336,6 @@ static void __init process_memory_node(const void *fdt, 
> int node,
>      }
>  }
>  
> -static void __init process_cpu_node(const void *fdt, int node,
> -                                    const char *name,
> -                                    u32 address_cells, u32 size_cells)
> -{
> -    const struct fdt_property *prop;
> -    u32 cpuid;
> -    int len;
> -
> -    prop = fdt_get_property(fdt, node, "reg", &len);
> -    if ( !prop )
> -    {
> -        early_printk("fdt: node `%s': missing `reg' property\n", name);
> -        return;
> -    }
> -
> -    if ( len < sizeof (cpuid) )
> -    {
> -        dt_printk("fdt: node `%s': `reg` property length is too short\n",
> -                  name);
> -        return;
> -    }
> -
> -    cpuid = dt_read_number((const __be32 *)prop->data, 1);
> -
> -    /* TODO: handle non-contiguous CPU ID */
> -    if ( cpuid >= NR_CPUS )
> -    {
> -        dt_printk("fdt: node `%s': reg(0x%x) >= NR_CPUS(%d)\n",
> -                  name, cpuid, NR_CPUS);
> -        return;
> -    }
> -    cpumask_set_cpu(cpuid, &cpu_possible_map);
> -}
> -
>  static void __init process_multiboot_node(const void *fdt, int node,
>                                            const char *name,
>                                            u32 address_cells, u32 size_cells)
> @@ -435,8 +389,6 @@ static int __init early_scan_node(const void *fdt,
>  {
>      if ( device_tree_node_matches(fdt, node, "memory") )
>          process_memory_node(fdt, node, name, address_cells, size_cells);
> -    else if ( device_tree_type_matches(fdt, node, "cpu") )
> -        process_cpu_node(fdt, node, name, address_cells, size_cells);
>      else if ( device_tree_node_compatible(fdt, node, "xen,multiboot-module" 
> ) )
>          process_multiboot_node(fdt, node, name, address_cells, size_cells);
>  
> diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
> index b884354..5bc7259 100644
> --- a/xen/include/asm-arm/processor.h
> +++ b/xen/include/asm-arm/processor.h
> @@ -13,6 +13,7 @@
>  #define MPIDR_AFF0_SHIFT    (0)
>  #define MPIDR_AFF0_MASK     (0xff << MPIDR_AFF0_SHIFT)
>  #define MPIDR_HWID_MASK     0xffffff
> +#define MPIDR_INVALID       (~MPIDR_HWID_MASK)
>  
>  /* TTBCR Translation Table Base Control Register */
>  #define TTBCR_EAE    0x80000000
> @@ -234,6 +235,9 @@ extern void identify_cpu(struct cpuinfo_arm *);
>  extern struct cpuinfo_arm cpu_data[];
>  #define current_cpu_data cpu_data[smp_processor_id()]
>  
> +extern u32 __cpu_logical_map[];
> +#define cpu_logical_map(cpu) __cpu_logical_map[cpu]
> +
>  union hsr {
>      uint32_t bits;
>      struct {



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