From: Ashok Raj It is not required to choose the physflat mode when CPU hotplug is enabled and CPUs <=8 case. Use of genapic_flat with the mask version is capable of doing the same, instead of doing the send_IPI_mask_sequence() where its a unicast. This is another change that Andi introduced with the physflat mode. Signed-off-by: Ashok Raj Cc: Andi Kleen Signed-off-by: Andrew Morton --- arch/x86_64/kernel/genapic.c | 9 +-------- 1 files changed, 1 insertion(+), 8 deletions(-) diff -puN arch/x86_64/kernel/genapic.c~x86_64-choose-physflat-for-amd-systems-only-when-8-cpus arch/x86_64/kernel/genapic.c --- devel/arch/x86_64/kernel/genapic.c~x86_64-choose-physflat-for-amd-systems-only-when-8-cpus 2005-08-01 17:12:11.000000000 -0700 +++ devel-akpm/arch/x86_64/kernel/genapic.c 2005-08-01 17:12:11.000000000 -0700 @@ -69,15 +69,8 @@ void __init clustered_apic_check(void) } /* Don't use clustered mode on AMD platforms. */ - if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) { + if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && (num_cpus > 8)) { genapic = &apic_physflat; - /* In the CPU hotplug case we cannot use broadcast mode - because that opens a race when a CPU is removed. - Stay at physflat mode in this case. - AK */ -#ifdef CONFIG_HOTPLUG_CPU - if (num_cpus <= 8) - genapic = &apic_flat; -#endif goto print; } _