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    SubjectRe: [PATCH 3/3] x86, AMD: Disable wrongly set X86_FEATURE_LAHF_LM CPUID bit
    On 08/30/2009 12:30 PM, Borislav Petkov wrote:
    > On Sun, Aug 30, 2009 at 12:22:34PM -0700, H. Peter Anvin wrote:
    >> On 08/30/2009 04:50 AM, Borislav Petkov wrote:
    >>> clear_cpu_cap(c, X86_FEATURE_LAHF_LM);
    >>> + if (!rdmsrl_amd_safe(0xc001100d, &val)) {
    >>> + val &= ~(1ULL << 32);
    >>> + wrmsr_amd_safe(0xc001100d, (u32) val,
    >>> + (u32)(val >> 32));
    >>> + }
    >>> + }
    >> We presumably want/need wrmsrl_amd_safe() here!
    >
    > Actually, it is wrmsr_amd_safe() because we need the magic value in
    > %edi. wrmsr_amd_safe() calls the _regs variant with the array argument.
    > And we don't have a wrmsrl_amd_safe-one which gets a 64bit msr value as
    > an argument similar to the rdmsrl one.
    >

    That's exactly the point. We shouldn't have rdmsrl_amd_safe() on one
    hand and wrmsr_asm_safe() on the other. I have already fixed this up in
    my tree, but this kind of asymmetry should have been a big red flashing
    light.

    -hpa

    --
    H. Peter Anvin, Intel Open Source Technology Center
    I work for Intel. I don't speak on their behalf.



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