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    Subject[PATCH 14/24] x86/pkeys: Don't check if PKRU is zero before writting it
    Date
    write_pkru() checks if the current value is the same as the expected
    value. So instead just checking if the current and new value is zero
    (and skip the write in such a case) we can benefit from that.

    Remove the zero check of PKRU, write_pkru() provides a similar check.

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    ---
    arch/x86/mm/pkeys.c | 7 -------
    1 file changed, 7 deletions(-)

    diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
    index 05bb9a44eb1c3..50f65fc1b9a3f 100644
    --- a/arch/x86/mm/pkeys.c
    +++ b/arch/x86/mm/pkeys.c
    @@ -142,13 +142,6 @@ u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) |
    void copy_init_pkru_to_fpregs(void)
    {
    u32 init_pkru_value_snapshot = READ_ONCE(init_pkru_value);
    - /*
    - * Any write to PKRU takes it out of the XSAVE 'init
    - * state' which increases context switch cost. Avoid
    - * writing 0 when PKRU was already 0.
    - */
    - if (!init_pkru_value_snapshot && !read_pkru())
    - return;
    /*
    * Override the PKRU state that came from 'init_fpstate'
    * with the baseline from the process.
    --
    2.20.1
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