[PATCH 4.4 023/107] x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2018-07-23 12:46:29
Also in:
lkml
4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Woodhouse <redacted> (cherry picked from 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 <redacted> Signed-off-by: Thomas Gleixner <redacted> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Borislav Petkov <redacted> Acked-by: Dave Hansen <redacted> 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: David Woodhouse <redacted> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Srivatsa S. Bhat <redacted> Reviewed-by: Matt Helsley (VMware) <redacted> Reviewed-by: Alexey Makhalov <redacted> Reviewed-by: Bo Gan <redacted> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- arch/x86/kernel/cpu/common.c | 48 ++++++++++++++++++++++++++++++++++++++----- 1 file changed, 43 insertions(+), 5 deletions(-)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c@@ -43,6 +43,8 @@ #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>
@@ -794,6 +796,41 @@ static void identify_cpu_without_cpuid(s #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,
@@ -840,11 +877,12 @@ static void __init early_identify_cpu(st 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);