x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown
authorDavid Woodhouse <dwmw@amazon.co.uk>
Thu, 25 Jan 2018 16:14:13 +0000 (16:14 +0000)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 7 Feb 2018 19:12:19 +0000 (11:12 -0800)
commit fec9434a12f38d3aeafeb75711b71d8a1fdef621

Also, for CPUs which don't speculate at all, don't report that they're
vulnerable to the Spectre variants either.

Leave the cpu_no_meltdown[] match table with just X86_VENDOR_AMD in it
for now, even though that could be done with a simple comparison, on the
assumption that we'll have more to add.

Based on suggestions from Dave Hansen and Alan Cox.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: ak@linux.intel.com
Cc: ashok.raj@intel.com
Cc: karahmed@amazon.de
Cc: arjan@linux.intel.com
Cc: torvalds@linux-foundation.org
Cc: peterz@infradead.org
Cc: bp@alien8.de
Cc: pbonzini@redhat.com
Cc: tim.c.chen@linux.intel.com
Cc: gregkh@linux-foundation.org
Link: https://lkml.kernel.org/r/1516896855-7642-6-git-send-email-dwmw@amazon.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/x86/kernel/cpu/common.c

index e5d66e93ed811534ed1abfaf16d1ca2c38d3655d..970ee06dc8aad645dc80d1a8f839aad4f667181e 100644 (file)
@@ -47,6 +47,8 @@
 #include <asm/pat.h>
 #include <asm/microcode.h>
 #include <asm/microcode_intel.h>
+#include <asm/intel-family.h>
+#include <asm/cpu_device_id.h>
 
 #ifdef CONFIG_X86_LOCAL_APIC
 #include <asm/uv/uv.h>
@@ -853,6 +855,41 @@ static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
 #endif
 }
 
+static const __initdata struct x86_cpu_id cpu_no_speculation[] = {
+       { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_CEDARVIEW,   X86_FEATURE_ANY },
+       { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_CLOVERVIEW,  X86_FEATURE_ANY },
+       { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_LINCROFT,    X86_FEATURE_ANY },
+       { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_PENWELL,     X86_FEATURE_ANY },
+       { X86_VENDOR_INTEL,     6, INTEL_FAM6_ATOM_PINEVIEW,    X86_FEATURE_ANY },
+       { X86_VENDOR_CENTAUR,   5 },
+       { X86_VENDOR_INTEL,     5 },
+       { X86_VENDOR_NSC,       5 },
+       { X86_VENDOR_ANY,       4 },
+       {}
+};
+
+static const __initdata struct x86_cpu_id cpu_no_meltdown[] = {
+       { X86_VENDOR_AMD },
+       {}
+};
+
+static bool __init cpu_vulnerable_to_meltdown(struct cpuinfo_x86 *c)
+{
+       u64 ia32_cap = 0;
+
+       if (x86_match_cpu(cpu_no_meltdown))
+               return false;
+
+       if (cpu_has(c, X86_FEATURE_ARCH_CAPABILITIES))
+               rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);
+
+       /* Rogue Data Cache Load? No! */
+       if (ia32_cap & ARCH_CAP_RDCL_NO)
+               return false;
+
+       return true;
+}
+
 /*
  * Do minimum CPU detection early.
  * Fields really needed: vendor, cpuid_level, family, model, mask,
@@ -900,11 +937,12 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 
        setup_force_cpu_cap(X86_FEATURE_ALWAYS);
 
-       if (c->x86_vendor != X86_VENDOR_AMD)
-               setup_force_cpu_bug(X86_BUG_CPU_MELTDOWN);
-
-       setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
-       setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
+       if (!x86_match_cpu(cpu_no_speculation)) {
+               if (cpu_vulnerable_to_meltdown(c))
+                       setup_force_cpu_bug(X86_BUG_CPU_MELTDOWN);
+               setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
+               setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
+       }
 
        fpu__init_system(c);