x86, apic: Use logical flat on intel with <= 8 logical cpus
On Intel platforms, 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.
Fix the relevant comments while we are at it.
We can clean up default_setup_apic_routing() by using apic->probe()
but that is a different item.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: "yinghai@kernel.org" <yinghai@kernel.org>
LKML-Reference: <1253327399.3948.747.camel@sbs-t61.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 79e5b92..072aea6 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -61,7 +61,7 @@
/*
* The highest APIC ID seen during enumeration.
*
- * This determines the messaging protocol we can use: if all APIC IDs
+ * On AMD, 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).
*
@@ -1915,24 +1915,14 @@
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 <ashok.raj@intel.com>
- */
- if (max_physical_apicid >= 8) {
- switch (boot_cpu_data.x86_vendor) {
- case X86_VENDOR_INTEL:
- if (!APIC_XAPIC(version)) {
- def_to_bigsmp = 0;
- break;
- }
- /* If P4 and above fall through */
- case X86_VENDOR_AMD:
+ switch (boot_cpu_data.x86_vendor) {
+ case X86_VENDOR_INTEL:
+ if (num_processors > 8)
def_to_bigsmp = 1;
- }
+ break;
+ case X86_VENDOR_AMD:
+ if (max_physical_apicid >= 8)
+ def_to_bigsmp = 1;
}
#endif
diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c
index 65edc18..c4cbd308 100644
--- a/arch/x86/kernel/apic/probe_64.c
+++ b/arch/x86/kernel/apic/probe_64.c
@@ -64,16 +64,23 @@
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)
- apic = &apic_physflat;
- printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
+ switch (boot_cpu_data.x86_vendor) {
+ case X86_VENDOR_INTEL:
+ if (num_processors > 8)
+ apic = &apic_physflat;
+ break;
+ case X86_VENDOR_AMD:
+ if (max_physical_apicid >= 8)
+ apic = &apic_physflat;
+ }
}
+ printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
+
if (is_vsmp_box()) {
/* need to update phys_pkg_id */
apic->phys_pkg_id = apicid_phys_pkg_id;