On Mon, Aug 20, 2007 at 09:06:27AM +0100, Thiemo Seufer wrote: > > It seems the rdhwr emulation is used/proposed for accessing the thread > > word in NPTL. > > I've been reading some of the posts from 2005 about this choice of this > > and what I have missed is anyone talking about using the "k0" register > > for TLS. It seems logical that the kernel could always restore k0 on > > returning to user-land and having k1 only for the last part of returning > > to user is sufficient. Any reason why this was not looked at? > > The TLB handlers need k0/k1 as well and have no good place to save/restore > a register. It can be done but would require several extra instructions in the most performance sensitive parts of the OS. Aside, latest MIPS processors support a hardware implementation of rdhwr $29, so there is no more emulation overhead for this instruction at full binary compatibility. Ralf
