This patch adds the ability to be able to save the FPU registers to the
thread struct without giving up (disabling the facility) next time the
process returns to userspace.
This patch optimises the thread copy path (as a result of a fork() or
clone()) so that the parent thread can return to userspace with hot
registers avoiding a possibly pointless reload of FPU register state.
Signed-off-by: Cyril Bur <cyril...@gmail.com>
---
arch/powerpc/include/asm/switch_to.h | 2 +-
arch/powerpc/kernel/fpu.S | 21 ++++------------
arch/powerpc/kernel/process.c | 46 +++++++++++++++++++++++++++++++++++-
3 files changed, 50 insertions(+), 19 deletions(-)
diff --git a/arch/powerpc/include/asm/switch_to.h
b/arch/powerpc/include/asm/switch_to.h
index 171ce13..8cf7fd6 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -28,7 +28,7 @@ extern void giveup_all(struct task_struct *);
extern void enable_kernel_fp(void);
extern void flush_fp_to_thread(struct task_struct *);
extern void giveup_fpu(struct task_struct *);
-extern void __giveup_fpu(struct task_struct *);
+extern void save_fpu(struct task_struct *);
static inline void disable_kernel_fp(void)
{
msr_check_and_clear(MSR_FP);
diff --git a/arch/powerpc/kernel/fpu.S b/arch/powerpc/kernel/fpu.S
index b063524..15da2b5 100644
--- a/arch/powerpc/kernel/fpu.S
+++ b/arch/powerpc/kernel/fpu.S
@@ -143,33 +143,20 @@ END_FTR_SECTION_IFSET(CPU_FTR_VSX)
blr
/*
- * __giveup_fpu(tsk)
- * Disable FP for the task given as the argument,
- * and save the floating-point registers in its thread_struct.
+ * save_fpu(tsk)
+ * Save the floating-point registers in its thread_struct.
* Enables the FPU for use in the kernel on return.
*/
-_GLOBAL(__giveup_fpu)
+_GLOBAL(save_fpu)
addi r3,r3,THREAD /* want THREAD of task */
PPC_LL r6,THREAD_FPSAVEAREA(r3)
PPC_LL r5,PT_REGS(r3)
PPC_LCMPI 0,r6,0
bne 2f
addi r6,r3,THREAD_FPSTATE
-2: PPC_LCMPI 0,r5,0
- SAVE_32FPVSRS(0, R4, R6)
+2: SAVE_32FPVSRS(0, R4, R6)
mffs fr0
stfd fr0,FPSTATE_FPSCR(r6)
- beq 1f
- PPC_LL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
- li r3,MSR_FP|MSR_FE0|MSR_FE1
-#ifdef CONFIG_VSX
-BEGIN_FTR_SECTION
- oris r3,r3,MSR_VSX@h
-END_FTR_SECTION_IFSET(CPU_FTR_VSX)
-#endif
- andc r4,r4,r3 /* disable FP for previous task */
- PPC_STL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
-1:
blr
/*
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index c602b67..51e246a 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -133,6 +133,16 @@ void __msr_check_and_clear(unsigned long bits)
EXPORT_SYMBOL(__msr_check_and_clear);
#ifdef CONFIG_PPC_FPU
+void __giveup_fpu(struct task_struct *tsk)
+{
+ save_fpu(tsk);
+ tsk->thread.regs->msr &= ~MSR_FP;
+#ifdef CONFIG_VSX
+ if (cpu_has_feature(CPU_FTR_VSX))
+ tsk->thread.regs->msr &= ~MSR_VSX;
+#endif
+}
+
void giveup_fpu(struct task_struct *tsk)
{
check_if_tm_restore_required(tsk);
@@ -413,12 +423,46 @@ void restore_math(struct pt_regs *regs)
regs->msr = msr;
}
+void save_all(struct task_struct *tsk)
+{
+ unsigned long usermsr;
+
+ if (!tsk->thread.regs)
+ return;
+
+ usermsr = tsk->thread.regs->msr;
+
+ if ((usermsr & msr_all_available) == 0)
+ return;
+
+ msr_check_and_set(msr_all_available);
+
+#ifdef CONFIG_PPC_FPU
+ if (usermsr & MSR_FP)
+ save_fpu(tsk);
+#endif
+#ifdef CONFIG_ALTIVEC
+ if (usermsr & MSR_VEC)
+ __giveup_altivec(tsk);
+#endif
+#ifdef CONFIG_VSX
+ if (usermsr & MSR_VSX)
+ __giveup_vsx(tsk);
+#endif
+#ifdef CONFIG_SPE
+ if (usermsr & MSR_SPE)
+ __giveup_spe(tsk);
+#endif
+
+ msr_check_and_clear(msr_all_available);
+}
+
void flush_all_to_thread(struct task_struct *tsk)
{
if (tsk->thread.regs) {
preempt_disable();
BUG_ON(tsk != current);
- giveup_all(tsk);
+ save_all(tsk);
#ifdef CONFIG_SPE
if (tsk->thread.regs->msr & MSR_SPE)
--
2.6.2
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