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x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown

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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
This commit is contained in:
David Woodhouse 2018-01-25 16:14:13 +00:00 committed by Thomas Gleixner
parent 1e340c60d0
commit fec9434a12
1 changed files with 43 additions and 5 deletions
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48
arch/x86/kernel/cpu/common.c
View 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);