On Wed, Jan 09, 2019 at 12:47:39PM +0100, Sebastian Andrzej Siewior wrote: > From: Rik van Riel <riel@xxxxxxxxxxx> > > The FPU registers need only to be saved if TIF_NEED_FPU_LOAD is not set. > Otherwise this has been already done and can be skipped. > > Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > --- > arch/x86/kernel/fpu/signal.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c > index bf4e6caad305e..a25be217f9a2c 100644 > --- a/arch/x86/kernel/fpu/signal.c > +++ b/arch/x86/kernel/fpu/signal.c > @@ -156,7 +156,16 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) > sizeof(struct user_i387_ia32_struct), NULL, > (struct _fpstate_32 __user *) buf) ? -1 : 1; > > - copy_fpregs_to_fpstate(fpu); > + __fpregs_changes_begin(); > + /* > + * If we do not need to load the FPU registers at return to userspace > + * then the CPU has the current state and we need to save it. Otherwise > + * it is already done and we can skip it. > + */ > + if (!test_thread_flag(TIF_NEED_FPU_LOAD)) > + copy_fpregs_to_fpstate(fpu); I wonder if this flag would make the code more easy to follow by calling it TIF_FPU_REGS_VALID instead, to denote that the FPU registers in the CPU have a valid content. Then the test becomes: if (test_thread_flag(TIF_FPU_REGS_VALID)) copy_fpregs_to_fpstate(fpu); -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.