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    Subject[tip:x86/xsave] x86, xsave: Track the offset, size of state in the xsave layout
    Commit-ID:  a1488f8bf4d72ad724700f6e982469a1240e4264
    Gitweb: http://git.kernel.org/tip/a1488f8bf4d72ad724700f6e982469a1240e4264
    Author: Suresh Siddha <suresh.b.siddha@intel.com>
    AuthorDate: Mon, 19 Jul 2010 16:05:48 -0700
    Committer: H. Peter Anvin <hpa@linux.intel.com>
    CommitDate: Mon, 19 Jul 2010 17:51:17 -0700

    x86, xsave: Track the offset, size of state in the xsave layout

    Subleaves of the cpuid vector 0xd provides the offset and size of different
    feature state that are managed by the xsave/xrstor. Track this for the upcoming
    usage during signal handling.

    Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
    LKML-Reference: <20100719230205.262987929@sbs-t61.sc.intel.com>
    Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
    ---
    arch/x86/kernel/xsave.c | 29 +++++++++++++++++++++++++++++
    1 files changed, 29 insertions(+), 0 deletions(-)

    diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
    index 9801498..4993caa 100644
    --- a/arch/x86/kernel/xsave.c
    +++ b/arch/x86/kernel/xsave.c
    @@ -21,6 +21,8 @@ struct _fpx_sw_bytes fx_sw_reserved;
    struct _fpx_sw_bytes fx_sw_reserved_ia32;
    #endif

    +static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;
    +
    /*
    * Check for the presence of extended state information in the
    * user fpstate pointer in the sigcontext.
    @@ -302,12 +304,39 @@ void __cpuinit xsave_init(void)
    }

    /*
    + * Record the offsets and sizes of different state managed by the xsave
    + * memory layout.
    + */
    +static void setup_xstate_features(void)
    +{
    + int eax, ebx, ecx, edx, leaf = 0x2;
    +
    + xstate_features = fls64(pcntxt_mask);
    + xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
    + xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));
    +
    + do {
    + cpuid_count(0xd, leaf, &eax, &ebx, &ecx, &edx);
    +
    + if (eax == 0)
    + break;
    +
    + xstate_offsets[leaf] = ebx;
    + xstate_sizes[leaf] = eax;
    +
    + leaf++;
    + } while (1);
    +}
    +
    +/*
    * setup the xstate image representing the init state
    */
    static void __init setup_xstate_init(void)
    {
    init_xstate_buf = alloc_bootmem(xstate_size);
    init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
    +
    + setup_xstate_features();
    }

    /*

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