From b9d16a2a21aa9c264a29dd84d6f7b03581517a03 Mon Sep 17 00:00:00 2001 From: Aravind Gopalakrishnan Date: Mon, 27 Apr 2015 10:25:51 -0500 Subject: [PATCH] x86/cpu/amd: Set X86_FEATURE_EXTD_APICID for future processors Decision to use a 4-bit mask or 8-bit mask in default_get_apic_id() is controlled by setting capability bit X86_FEATURE_EXTD_APICID. Currently, we detect extended APIC ID support by accessing Link Transaction Control register D18F0x68 in PCI config space. But, not even that is needed as we can safely postulate that future AMD processors will support 8-bit APIC IDs and we can simply set that feature bit on them, without the PCI access. Signed-off-by: Aravind Gopalakrishnan Signed-off-by: Borislav Petkov Cc: Borislav Petkov Cc: H. Peter Anvin Cc: Jacob Shin Cc: Paolo Bonzini Cc: Thomas Gleixner Cc: dave.hansen@linux.intel.com Cc: hecmargi@upv.es Cc: mgorman@suse.de Link: http://lkml.kernel.org/r/1430148351-9013-1-git-send-email-Aravind.Gopalakrishnan@amd.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/amd.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index e4cf63301ff4..94e7051fba1a 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -520,8 +520,16 @@ static void early_init_amd(struct cpuinfo_x86 *c) set_cpu_cap(c, X86_FEATURE_K6_MTRR); #endif #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_PCI) - /* check CPU config space for extended APIC ID */ - if (cpu_has_apic && c->x86 >= 0xf) { + /* + * ApicID can always be treated as an 8-bit value for AMD APIC versions + * >= 0x10, but even old K8s came out of reset with version 0x10. So, we + * can safely set X86_FEATURE_EXTD_APICID unconditionally for families + * after 16h. + */ + if (cpu_has_apic && c->x86 > 0x16) { + set_cpu_cap(c, X86_FEATURE_EXTD_APICID); + } else if (cpu_has_apic && c->x86 >= 0xf) { + /* check CPU config space for extended APIC ID */ unsigned int val; val = read_pci_config(0, 24, 0, 0x68); if ((val & ((1 << 17) | (1 << 18))) == ((1 << 17) | (1 << 18))) -- 2.20.1