From bb668da6d6f2bec8a63838c098d9515eccb22cc4 Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Mon, 18 Jan 2010 12:10:49 -0800 Subject: [PATCH] x86, apic: use logical flat for systems with <= 8 logical cpus We can use logical flat mode if there are <= 8 logical cpu's (irrespective of physical apic id values). This will enable simplified and efficient IPI and device interrupt routing on such platforms. This has been tested to work on both Intel and AMD platforms. Exceptions like IBM summit platform which can't use logical flat mode are addressed by using OEM platform checks. Signed-off-by: Suresh Siddha Signed-off-by: Yinghai Lu Cc: Ananth N Mavinakayanahalli Cc: Chris McDermott Signed-off-by: Linus Torvalds --- arch/x86/kernel/apic/apic.c | 15 +-------------- arch/x86/kernel/apic/probe_64.c | 8 +++----- 2 files changed, 4 insertions(+), 19 deletions(-) diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index e80f291472a..3987e4408f7 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -61,12 +61,6 @@ unsigned int boot_cpu_physical_apicid = -1U; /* * 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; @@ -1898,14 +1892,7 @@ void __cpuinit generic_processor_info(int apicid, int version) max_physical_apicid = apicid; #ifdef CONFIG_X86_32 - /* - * Would be preferable to switch to bigsmp when CONFIG_HOTPLUG_CPU=y - * but we need to work other dependencies like SMP_SUSPEND etc - * before this can be done without some confusion. - * if (CPU_HOTPLUG_ENABLED || num_processors > 8) - * - Ashok Raj - */ - if (max_physical_apicid >= 8) { + if (num_processors > 8) { switch (boot_cpu_data.x86_vendor) { case X86_VENDOR_INTEL: if (!APIC_XAPIC(version)) { diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c index 65edc180fc8..450fe2064a1 100644 --- a/arch/x86/kernel/apic/probe_64.c +++ b/arch/x86/kernel/apic/probe_64.c @@ -64,15 +64,13 @@ void __init default_setup_apic_routing(void) apic = &apic_x2apic_phys; else apic = &apic_x2apic_cluster; - printk(KERN_INFO "Setting APIC routing to %s\n", apic->name); } #endif - if (apic == &apic_flat) { - if (max_physical_apicid >= 8) + if (apic == &apic_flat && num_processors > 8) apic = &apic_physflat; - printk(KERN_INFO "Setting APIC routing to %s\n", apic->name); - } + + printk(KERN_INFO "Setting APIC routing to %s\n", apic->name); if (is_vsmp_box()) { /* need to update phys_pkg_id */ -- 2.20.1