On Wed, Oct 24, 2018 at 12:13 PM Bae, Chang Seok <[email protected]> wrote: > > On Tue, Sep 18, 2018 at 12:02 PM Andy Lutomirski <[email protected]> > > On Tue, Sep 18, 2018 at 4:09 PM Chang S. Bae <[email protected]> > > wrote: > > > > > > With new helpers, FS/GS base access is centralized. > > > Eventually, when FSGSBASE instruction enabled, it will be faster. > > > > Sorry for not catching this during review, but: > > > > > +void x86_fsbase_write_cpu(unsigned long fsbase) { > > > + /* > > > + * Set the selector to 0 as a notion, that the segment base is > > > + * overwritten, which will be checked for skipping the segment > > > load > > > + * during context switch. > > > + */ > > > + loadseg(FS, 0); > > > > ^^^ > > > > what? > > > > > + wrmsrl(MSR_FS_BASE, fsbase); > > > +} > > > > I don't understand what the comment is trying to say, but the sole caller > > so far > > of this function is x86_gsbase_write_task(), and the code looks incorrect. > > > > Ingo, I think we need to address this during this merge window, probably by > > removing the comment and the loadseg() call (and the same for > > gsbase...inactive). But first, Chang, can you explain what exactly your > > intent is > > here? > > It's coming from do_arch_prctl_64(). If you think it really makes confusion in > x86_fsbase_write_cpu(), how about moving it to x86_fsbase_write_task()?
Why should ..write_task() magically change the index but only if it's writing current? I think you should move it all the way out to the caller (do_arch_prctl_64()?) and we can see if it makes sense there. > > Chang
