Date: Sat, 10 Jun 2000 12:51:46 -0600
From: Gareth Hughes <gareth@precisioninsight.com>
Here are the patches against 2.4.0-test1-ac12 for the fixes to the PIII
SSE/FXSR support.
Sorry, but I don't think this is right:
#define save_fpu(tsk) do { \
- asm volatile("fxsave %0 ; fwait" \
- : "=m" (tsk->thread.i387.hard)); \
+ asm volatile("fnstenv %0 ; fxsave %1 ; fwait" \
+ : "=m" (tsk->thread.i387.hard), \
+ "=m" (tsk->thread.i387.hard.fxsr_space[0])); \
If I'm not mistaken this means that you've added an additional
overhead on *every* task switch between FPU-using tasks. Instead you
should only convert to the old fsave format when that's actually
needed:
1. When setting up a signal context for invoking a signal handler.
2. For the PTRACE_GETFPREGS request.
I also don't understand why you expose the strange user_xfpregs_struct
format via the PTRACE_{GET,SET}XFPREGS requests. Why don't you just
provide the 512-byte FXSAVE area?
All in all, I think that the origional code in 2.4.0test1 is much
closer to what the endresult should look like. Just add the
PTRACE_{GET,SET}XFPREGS requests that return, write the FXSAVE data
(should be *very* simple), add the necessary bits for setting up the
signal frame (more or less what's in your patch, but this is the place
where the FXSAVE -> FSAVE conversion should be done), and add some
code to the core dumping code to add an extra note with the FXSAVE
area.
Mark
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