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    SubjectRe: [patch 0/8] x86/fpu: Mop up XSAVES and related damage
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    On Wed, Jun 02 2021 at 14:28, Yu-cheng Yu wrote:
    > On 6/2/2021 2:55 AM, Thomas Gleixner wrote:
    >
    > With the series applied, glibc pkey test fails sometimes. I will try to
    > find out the cause.

    That fails not sometimes. It fails always due to patch 7/8. The reason
    is that before that patch fpu__clear_all() reinitialized the hardware
    which includes writing the initial PKRU value.

    But fpu__initialize() does not store the initial PKRU value in the
    task's xstate which breaks PKRU. As that patch is not urgent we can
    postpone it for not.

    But looking at the above, it's not clear to me why that PKRU stuff works
    at all (upstream), but I'll figure it out eventually. I'm quite sure
    that it does work by pure chance not by design.

    Thanks,

    tglx

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