From cc97ab235f3fe32401ca198cebe6f42642e95770 Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Wed, 7 Nov 2018 23:13:59 +0000 Subject: MIPS: Simplify FP context initialization MIPS has up until now had 3 different ways for a task's floating point context to be initialized: - If the task's first use of FP involves it gaining ownership of an FPU then _init_fpu() is used to initialize the FPU's registers such that they all contain ~0, and the FPU registers will be stored to struct thread_info later (eg. when context switching). - If the task first uses FP on a CPU without an associated FPU then fpu_emulator_init_fpu() initializes the task's floating point register state in struct thread_info such that all floating point register contain the bit pattern 0x7ff800007ff80000, different to the _init_fpu() behaviour. - If a task's floating point context is first accessed via ptrace then init_fp_ctx() initializes the floating point register state in struct thread_info to ~0, giving equivalent state to _init_fpu(). The _init_fpu() path has 2 separate implementations - one for r2k/r3k style systems & one for r4k style systems. The _init_fpu() path also requires that we be careful to clear & restore the value of the Config5.FRE bit on modern systems in order to avoid inadvertently triggering floating point exceptions. None of this code is in a performance critical hot path - it runs only the first time a task uses floating point. As such it doesn't seem to warrant the complications of maintaining the _init_fpu() path. Remove _init_fpu() & fpu_emulator_init_fpu(), instead using init_fp_ctx() consistently to initialize floating point register state in struct thread_info. Upon a task's first use of floating point this will typically mean that we initialize state in memory & then load it into FPU registers using _restore_fp() just as we would on a context switch. For other paths such as __compute_return_epc_for_insn() or mipsr2_decoder() this results in a significant simplification of the work to be done. Signed-off-by: Paul Burton Patchwork: https://patchwork.linux-mips.org/patch/21002/ Cc: linux-mips@linux-mips.org --- arch/mips/loongson64/loongson-3/cop2-ex.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) (limited to 'arch/mips/loongson64') diff --git a/arch/mips/loongson64/loongson-3/cop2-ex.c b/arch/mips/loongson64/loongson-3/cop2-ex.c index 621d6af5f6eb..9efdfe430ff0 100644 --- a/arch/mips/loongson64/loongson-3/cop2-ex.c +++ b/arch/mips/loongson64/loongson-3/cop2-ex.c @@ -43,11 +43,8 @@ static int loongson_cu2_call(struct notifier_block *nfb, unsigned long action, /* If FPU is owned, we needn't init or restore fp */ if (!fpu_owned) { set_thread_flag(TIF_USEDFPU); - if (!used_math()) { - _init_fpu(current->thread.fpu.fcr31); - set_used_math(); - } else - _restore_fp(current); + init_fp_ctx(current); + _restore_fp(current); } preempt_enable(); -- cgit v1.2.3