Re: [Xen-devel] [PATCH v1 1/3] x86: identifying the boot cpu

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 03/12/2015 10:55 AM, Uma Sharma wrote:
> Provide helpers to access the socket and core IDs, resulting from 
> identification phase.
> Initialize socket and core ID to -1 i.e invalid instead of 0.
>
> Signed-off-by: Uma Sharma <uma.sharma523@xxxxxxxxx>
> ---
>   xen/arch/x86/setup.c            | 7 +++++--
>   xen/arch/x86/smpboot.c          | 3 ++-
>   xen/include/asm-x86/processor.h | 2 ++
>   3 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index 7593533..251840f 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -1259,6 +1259,11 @@ void __init noreturn __start_xen(unsigned long mbi_p)
>       microcode_grab_module(module_map, mbi, bootstrap_map);
>   
>       timer_init();
> +    /*
> +     * Identify the boot CPU, in case the scheduler initialization
> +     * needs to know about it (e.g., topology, etc.)
> +     */
> +    identify_cpu(&boot_cpu_data);
>   
>       init_idle_domain();
>   
> @@ -1270,8 +1275,6 @@ void __init noreturn __start_xen(unsigned long mbi_p)
>   
>       arch_init_memory();
>   
> -    identify_cpu(&boot_cpu_data);
> -
>       if ( cpu_has_fxsr )
>           set_in_cr4(X86_CR4_OSFXSR);
>       if ( cpu_has_xmm )
> diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
> index 314e253..6ec15e2 100644
> --- a/xen/arch/x86/smpboot.c
> +++ b/xen/arch/x86/smpboot.c
> @@ -59,7 +59,8 @@ DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_core_mask);
>   cpumask_t cpu_online_map __read_mostly;
>   EXPORT_SYMBOL(cpu_online_map);
>   
> -struct cpuinfo_x86 cpu_data[NR_CPUS];
> +struct cpuinfo_x86 cpu_data[NR_CPUS] =
> +        { [0 ... NR_CPUS-1] = { .phys_proc_id=-1, .cpu_core_id=-1 } };
I think these need to be initialized to BAD_APICID since that's what 
these fields are typically set to when no information is available.
(Or perhaps new macros should be defined and code that used to set these 
fields to BAD_APICID updated accordingly)
-boris


>   
>   u32 x86_cpu_to_apicid[NR_CPUS] __read_mostly =
>         { [0 ... NR_CPUS-1] = BAD_APICID };
> diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
> index 87d80ff..6ec9588 100644
> --- a/xen/include/asm-x86/processor.h
> +++ b/xen/include/asm-x86/processor.h
> @@ -214,7 +214,9 @@ extern void detect_extended_topology(struct cpuinfo_x86 *c);
>   
>   extern void detect_ht(struct cpuinfo_x86 *c);
>   
> +#define boot_cpu_to_core()   (boot_cpu_data.cpu_core_id)
>   #define cpu_to_core(_cpu)   (cpu_data[_cpu].cpu_core_id)
> +#define boot_cpu_to_socket() (boot_cpu_data.phys_proc_id)
>   #define cpu_to_socket(_cpu) (cpu_data[_cpu].phys_proc_id)
>   
>   unsigned int apicid_to_socket(unsigned int);

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