On 2019-01-30 12:56:14 [+0100], Borislav Petkov wrote: > > 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); I've been asked to add comment above the sequence so it is understood. I think the general approach is easy to follow once the concept is understood. I don't mind renaming the TIF_ thingy once again (it happend once or twice and I think the current one was suggested by Andy unless I mixed things up). The problem I have with the above is that if (test_thread_flag(TIF_NEED_FPU_LOAD)) do_that() becomes if (!test_thread_flag(TIF_FPU_REGS_VALID)) do_that() and you could argue again the other way around. So do we want NEED_LOAD or NEED_SAVE flag which is another way of saying REGS_VALID? More importantly the logic is changed when the bit is set and this requires more thinking than just doing sed on the patch series. Sebastian
