On 2019-01-30 12:55:07 [+0100], Borislav Petkov wrote: > This definitely needs to be written somewhere in > > arch/x86/include/asm/fpu/internal.h > > or where we decide to put the FPU handling rules. Added: Index: staging/arch/x86/include/asm/fpu/internal.h =================================================================== --- staging.orig/arch/x86/include/asm/fpu/internal.h +++ staging/arch/x86/include/asm/fpu/internal.h @@ -537,6 +537,12 @@ static inline void __fpregs_load_activat * * The FPU context is only stored/restore for user task and ->mm is used to * distinguish between kernel and user threads. + * + * If TIF_NEED_FPU_LOAD is cleared then CPU's FPU registers are holding the + * current content of current()'s FPU register state. + * If TIF_NEED_FPU_LOAD is set then CPU's FPU registers may not hold current()'s + * FPU registers. It is required to load the register before returning to + * userland or using the content otherwise. */ static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu) Sebastian
