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    Subject[PATCH v2 1/2] x86/fpu: Add helper function for tracking AVX512 status
    Date
    This commit adds a new helper function 'fpu_update_avx_timestamp' to
    perform the logic from tracking AVX512 feature use.

    Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
    ---
    Since Borislav Petkov is concerned about adding more macro masks and
    inlining the AVX512 status this patch adds a new helper function. This
    patch does not change the behavior of the current AVX512 status.

    arch/x86/include/asm/fpu/xstate.h | 1 +
    arch/x86/kernel/fpu/core.c | 6 ++----
    arch/x86/kernel/fpu/xstate.c | 13 +++++++++++++
    3 files changed, 16 insertions(+), 4 deletions(-)

    diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
    index 109dfcc75299..fe84ac5fb039 100644
    --- a/arch/x86/include/asm/fpu/xstate.h
    +++ b/arch/x86/include/asm/fpu/xstate.h
    @@ -134,6 +134,7 @@ extern u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];
    extern void __init update_regset_xstate_info(unsigned int size,
    u64 xstate_mask);

    +void fpu_update_avx_timestamp(struct fpu *fpu);
    void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr);
    int xfeature_size(int xfeature_nr);
    int copy_uabi_from_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf);
    diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
    index 7ada7bd03a32..6dbf3ee642f9 100644
    --- a/arch/x86/kernel/fpu/core.c
    +++ b/arch/x86/kernel/fpu/core.c
    @@ -102,11 +102,9 @@ void save_fpregs_to_fpstate(struct fpu *fpu)
    os_xsave(&fpu->state.xsave);

    /*
    - * AVX512 state is tracked here because its use is
    - * known to slow the max clock speed of the core.
    + * Track of the state of desired avx related xfeatures.
    */
    - if (fpu->state.xsave.header.xfeatures & XFEATURE_MASK_AVX512)
    - fpu->avx512_timestamp = jiffies;
    + fpu_update_avx_timestamp(fpu);
    return;
    }

    diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
    index c8def1b7f8fb..00b495914be2 100644
    --- a/arch/x86/kernel/fpu/xstate.c
    +++ b/arch/x86/kernel/fpu/xstate.c
    @@ -1245,6 +1245,19 @@ void xrstors(struct xregs_state *xstate, u64 mask)
    WARN_ON_ONCE(err);
    }

    +/*
    + * Track of the state of desired avx architecture features.
    + */
    +void fpu_update_avx_timestamp(struct fpu *fpu)
    +{
    + /*
    + * AVX512 state is tracked here because its use is known to slow
    + * the max clock speed of the core.
    + */
    + if (fpu->state.xsave.header.xfeatures & XFEATURE_MASK_AVX512)
    + fpu->avx512_timestamp = jiffies;
    +}
    +
    #ifdef CONFIG_PROC_PID_ARCH_STATUS
    /*
    * Report the amount of time elapsed in millisecond since last AVX512
    --
    2.25.1
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