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    SubjectRe: [PATCH v29 23/32] x86/cet/shstk: Add user-mode shadow stack support
    On Fri, Aug 27, 2021 at 11:37:34AM -0700, Yu, Yu-cheng wrote:
    > Right now, the kernel does lazy restore, and it waits until right before a
    > task goes back to ring-3 to restore xstates. If a task needs to write to
    > any xstate registers before that (e.g. for signals), it restores the whole
    > xstates first and clears TIF_NEED_FPU_LOAD, which will prevent xstates being
    > restored again later.

    shstk_setup() allocates a shadow stack for the task and puts its pointer
    in MSR_IA32_PL3_SSP.

    What does that have to do with a task having to write any xstate
    registers?

    --
    Regards/Gruss,
    Boris.

    https://people.kernel.org/tglx/notes-about-netiquette

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