From: Yinghai Lu Date: Wed, 5 Jan 2011 00:38:52 +0000 (-0800) Subject: x86: Fix APIC ID sizing bug on larger systems, clean up MAX_APICS confusion X-Git-Tag: v2.6.38-rc1~486^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cb2ded37fd2e1039f96c8c892da024a8f033add5;p=pandora-kernel.git x86: Fix APIC ID sizing bug on larger systems, clean up MAX_APICS confusion Found one x2apic pre-enabled system, x2apic_mode suddenly get corrupted after register some cpus, when compiled CONFIG_NR_CPUS=255 instead of 512. It turns out that generic_processor_info() ==> phyid_set(apicid, phys_cpu_present_map) causes the problem. phys_cpu_present_map is sized by MAX_APICS bits, and pre-enabled system some cpus have an apic id > 255. The variable after phys_cpu_present_map may get corrupted silently: ffffffff828e8420 B phys_cpu_present_map ffffffff828e8440 B apic_verbosity ffffffff828e8444 B local_apic_timer_c2_ok ffffffff828e8448 B disable_apic ffffffff828e844c B x2apic_mode ffffffff828e8450 B x2apic_disabled ffffffff828e8454 B num_processors ... Actually phys_cpu_present_map is referenced via apic id, instead index. We should use MAX_LOCAL_APIC instead MAX_APICS. For 64-bit it will be 32768 in all cases. BSS will increase by 4k bytes on 64-bit: text data bss dec filename 21696943 4193748 12787712 38678403 vmlinux.before 21696943 4193748 12791808 38682499 vmlinux.after No change on 32bit. Finally we can remove MAX_APCIS that was rather confusing. Signed-off-by: Yinghai Lu Cc: H. Peter Anvin Cc: "Eric W. Biederman" LKML-Reference: <4D23BD9C.3070102@kernel.org> Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed