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    SubjectRe: [RFC PATCH 04/11] x86,fpu: defer FPU restore until return to userspace
    On 01/11, riel@redhat.com wrote:
    >
    > Defer restoring the FPU state, if so desired, until the task returns to
    > userspace.

    And yet another concern ;) Although I feel that I am totally confused and
    probably wrong.

    > --- a/arch/x86/include/asm/fpu-internal.h
    > +++ b/arch/x86/include/asm/fpu-internal.h
    > @@ -382,6 +382,7 @@ static inline void drop_init_fpu(struct task_struct *tsk)
    > else
    > fxrstor_checking(&init_xstate_buf->i387);
    > }
    > + clear_thread_flag(TIF_LOAD_FPU);
    > }

    OK, but shouldn't (say) restore_user_xstate() clear TIF_LOAD_FPU too?
    Otherwise, can't switch_fpu_finish() restore the wrong context later?

    Or. Perhaps switch_fpu_finish() should do nothing if fpu.has_fpu == T,
    I dunno.

    Oleg.



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