From 48fd5b5ee714714f4cf9f9e1cba3b49b1fd40ed6 Mon Sep 17 00:00:00 2001 From: Tony Luck Date: Thu, 16 Apr 2020 13:57:53 -0700 Subject: x86/split_lock: Bits in IA32_CORE_CAPABILITIES are not architectural The Intel Software Developers' Manual erroneously listed bit 5 of the IA32_CORE_CAPABILITIES register as an architectural feature. It is not. Features enumerated by IA32_CORE_CAPABILITIES are model specific and implementation details may vary in different cpu models. Thus it is only safe to trust features after checking the CPU model. Icelake client and server models are known to implement the split lock detect feature even though they don't enumerate IA32_CORE_CAPABILITIES [ tglx: Use switch() for readability and massage comments ] Fixes: 6650cdd9a8cc ("x86/split_lock: Enable split lock detection by kernel") Signed-off-by: Tony Luck Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200416205754.21177-3-tony.luck@intel.com --- arch/x86/kernel/cpu/intel.c | 45 +++++++++++++++++++++++++++++++-------------- 1 file changed, 31 insertions(+), 14 deletions(-) (limited to 'arch') diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index ec0d8c74932f..c23ad481347e 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -1120,10 +1120,17 @@ void switch_to_sld(unsigned long tifn) } /* - * The following processors have the split lock detection feature. But - * since they don't have the IA32_CORE_CAPABILITIES MSR, the feature cannot - * be enumerated. Enable it by family and model matching on these - * processors. + * Bits in the IA32_CORE_CAPABILITIES are not architectural, so they should + * only be trusted if it is confirmed that a CPU model implements a + * specific feature at a particular bit position. + * + * The possible driver data field values: + * + * - 0: CPU models that are known to have the per-core split-lock detection + * feature even though they do not enumerate IA32_CORE_CAPABILITIES. + * + * - 1: CPU models which may enumerate IA32_CORE_CAPABILITIES and if so use + * bit 5 to enumerate the per-core split-lock detection feature. */ static const struct x86_cpu_id split_lock_cpu_ids[] __initconst = { X86_MATCH_INTEL_FAM6_MODEL(ICELAKE_X, 0), @@ -1133,19 +1140,29 @@ static const struct x86_cpu_id split_lock_cpu_ids[] __initconst = { void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) { - u64 ia32_core_caps = 0; + const struct x86_cpu_id *m; + u64 ia32_core_caps; + + if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) + return; - if (c->x86_vendor != X86_VENDOR_INTEL) + m = x86_match_cpu(split_lock_cpu_ids); + if (!m) return; - if (cpu_has(c, X86_FEATURE_CORE_CAPABILITIES)) { - /* Enumerate features reported in IA32_CORE_CAPABILITIES MSR. */ + + switch (m->driver_data) { + case 0: + break; + case 1: + if (!cpu_has(c, X86_FEATURE_CORE_CAPABILITIES)) + return; rdmsrl(MSR_IA32_CORE_CAPS, ia32_core_caps); - } else if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) { - /* Enumerate split lock detection by family and model. */ - if (x86_match_cpu(split_lock_cpu_ids)) - ia32_core_caps |= MSR_IA32_CORE_CAPS_SPLIT_LOCK_DETECT; + if (!(ia32_core_caps & MSR_IA32_CORE_CAPS_SPLIT_LOCK_DETECT)) + return; + break; + default: + return; } - if (ia32_core_caps & MSR_IA32_CORE_CAPS_SPLIT_LOCK_DETECT) - split_lock_setup(); + split_lock_setup(); } -- cgit v1.2.3