From fdbecd9fd14198853bec4cbae8bc7af93f2e3de3 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sat, 31 Jan 2009 03:57:12 +0100 Subject: [PATCH] x86, apic: explain the purpose of max_physical_apicid Signed-off-by: Ingo Molnar --- arch/x86/kernel/apic.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/apic.c b/arch/x86/kernel/apic.c index a04a73a51d2..5475e1c3180 100644 --- a/arch/x86/kernel/apic.c +++ b/arch/x86/kernel/apic.c @@ -50,13 +50,26 @@ #include unsigned int num_processors; + unsigned disabled_cpus __cpuinitdata; + /* Processor that is doing the boot up */ unsigned int boot_cpu_physical_apicid = -1U; -EXPORT_SYMBOL(boot_cpu_physical_apicid); + +/* + * The highest APIC ID seen during enumeration. + * + * This determines the messaging protocol we can use: if all APIC IDs + * are in the 0 ... 7 range, then we can use logical addressing which + * has some performance advantages (better broadcasting). + * + * If there's an APIC ID above 8, we use physical addressing. + */ unsigned int max_physical_apicid; -/* Bitmask of physically existing CPUs */ +/* + * Bitmask of physically existing CPUs: + */ physid_mask_t phys_cpu_present_map; /* -- 2.11.4.GIT