lkml.org 
[lkml]   [2018]   [Jun]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Date
    Subject[PATCH 3.16 044/410] x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown
    3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: David Woodhouse <dwmw@amazon.co.uk>

    commit fec9434a12f38d3aeafeb75711b71d8a1fdef621 upstream.

    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: David Woodhouse <dwmw@amazon.co.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    [bwh: Backported to 3.16: adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    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
    @@ -41,6 +41,8 @@
    #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>
    @@ -761,6 +763,41 @@ 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,
    @@ -809,11 +846,12 @@ 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);
    + }
    }

    void __init early_cpu_init(void)
    \
     
     \ /
      Last update: 2018-06-07 16:54    [W:2.622 / U:0.784 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site