x86/speculation: Simplify the CPU bug detection logic

Only CPUs which speculate can speculate. Therefore, it seems prudent
to test for cpu_no_speculation first and only then determine whether
a specific speculating CPU is susceptible to store bypass speculation.
This is underlined by all CPUs currently listed in cpu_no_speculation
were present in cpu_no_spec_store_bypass as well.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: bp@suse.de
Cc: konrad.wilk@oracle.com
Link: https://lkml.kernel.org/r/20180522090539.GA24668@light.dominikbrodowski.net

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 78decc3e306712dbca3ffd4c71392f681ba9f5df..38276f58d3bfe2ce17d51450360be69c5ab70e43 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -942,12 +942,8 @@ static const __initconst struct x86_cpu_id cpu_no_meltdown[] = {
        {}
 };
 
+/* Only list CPUs which speculate but are non susceptible to SSB */
 static const __initconst struct x86_cpu_id cpu_no_spec_store_bypass[] = {
-       { X86_VENDOR_INTEL,     6,      INTEL_FAM6_ATOM_PINEVIEW        },
-       { X86_VENDOR_INTEL,     6,      INTEL_FAM6_ATOM_LINCROFT        },
-       { X86_VENDOR_INTEL,     6,      INTEL_FAM6_ATOM_PENWELL         },
-       { X86_VENDOR_INTEL,     6,      INTEL_FAM6_ATOM_CLOVERVIEW      },
-       { X86_VENDOR_INTEL,     6,      INTEL_FAM6_ATOM_CEDARVIEW       },
        { X86_VENDOR_INTEL,     6,      INTEL_FAM6_ATOM_SILVERMONT1     },
        { X86_VENDOR_INTEL,     6,      INTEL_FAM6_ATOM_AIRMONT         },
        { X86_VENDOR_INTEL,     6,      INTEL_FAM6_ATOM_SILVERMONT2     },
@@ -955,14 +951,10 @@ static const __initconst struct x86_cpu_id cpu_no_spec_store_bypass[] = {
        { X86_VENDOR_INTEL,     6,      INTEL_FAM6_CORE_YONAH           },
        { X86_VENDOR_INTEL,     6,      INTEL_FAM6_XEON_PHI_KNL         },
        { X86_VENDOR_INTEL,     6,      INTEL_FAM6_XEON_PHI_KNM         },
-       { X86_VENDOR_CENTAUR,   5,                                      },
-       { X86_VENDOR_INTEL,     5,                                      },
-       { X86_VENDOR_NSC,       5,                                      },
        { X86_VENDOR_AMD,       0x12,                                   },
        { X86_VENDOR_AMD,       0x11,                                   },
        { X86_VENDOR_AMD,       0x10,                                   },
        { X86_VENDOR_AMD,       0xf,                                    },
-       { X86_VENDOR_ANY,       4,                                      },
        {}
 };
 
@@ -970,6 +962,12 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
 {
        u64 ia32_cap = 0;
 
+       if (x86_match_cpu(cpu_no_speculation))
+               return;
+
+       setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
+       setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
+
        if (cpu_has(c, X86_FEATURE_ARCH_CAPABILITIES))
                rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);
 
@@ -977,12 +975,6 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
           !(ia32_cap & ARCH_CAP_SSB_NO))
                setup_force_cpu_bug(X86_BUG_SPEC_STORE_BYPASS);
 
-       if (x86_match_cpu(cpu_no_speculation))
-               return;
-
-       setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
-       setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
-
        if (x86_match_cpu(cpu_no_meltdown))
                return;