From fbfe9c847edf57ac8232aeafb290f272289893a3 Mon Sep 17 00:00:00 2001 From: Ingo van Lil Date: Wed, 14 Sep 2011 16:21:23 -0700 Subject: um: Save FPU registers between task switches Some time ago Jeff prepared 42daba316557 ("uml: stop saving process FP state") for UML to stop saving the process FP state between task switches. The assumption was that since with SKAS0 every guest process runs inside a host process context the host OS will take care of keeping the proper FP state. Unfortunately this is not true for multi-threaded applications, where all guest threads share a single host process context yet all may use the FPU on their own. Although I haven't verified it I suspect things to be even worse in SKAS3 mode where all guest processes run inside a single host process. The patch reintroduces the saving and restoring of the FP context between task switches. [richard@nod.at: Ingo posted this patch in 2009, sadly it was never applied and got lost. Now in 2011 the problem was reported by Gunnar.] Signed-off-by: Ingo van Lil Signed-off-by: Richard Weinberger Reported-by: Tested-by: Cc: Stanislav Meduna Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/kernel/process.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/um/kernel/process.c') diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c index fab4371184f..21c1ae7c3d7 100644 --- a/arch/um/kernel/process.c +++ b/arch/um/kernel/process.c @@ -202,7 +202,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, arch_copy_thread(¤t->thread.arch, &p->thread.arch); } else { - get_safe_registers(p->thread.regs.regs.gp); + get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp); p->thread.request.u.thread = current->thread.request.u.thread; handler = new_thread_handler; } -- cgit v1.2.3-70-g09d2