Subject: [PATCH V2 8/8] powerpc: Add the ability to save VSX without giving it up

From: Cyril Bur <[email-masked]>
Date: Fri, 15 Jan 2016 16:04:14 +1100

This patch adds the ability to be able to save the VSX registers to the
thread struct without giving up (disabling the facility) next time the
process returns to userspace.

This patch builds on a previous optimisation for the FPU and VEC registers
in the thread copy path to avoid a possibly pointless reload of VSX state.

Signed-off-by: Cyril Bur <[email-masked]>
---
 arch/powerpc/include/asm/switch_to.h |  1 -
 arch/powerpc/kernel/ppc_ksyms.c      |  4 ----
 arch/powerpc/kernel/process.c        | 23 ++++++++++++++++++-----
 arch/powerpc/kernel/vector.S         | 17 -----------------
 4 files changed, 18 insertions(+), 27 deletions(-)

diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index 29dda9d..4dfcd3e 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -52,7 +52,6 @@ static inline void disable_kernel_altivec(void)
 extern void enable_kernel_vsx(void);
 extern void flush_vsx_to_thread(struct task_struct *);
 extern void giveup_vsx(struct task_struct *);
-extern void __giveup_vsx(struct task_struct *);
 static inline void disable_kernel_vsx(void)
 {
 	msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);
diff --git a/arch/powerpc/kernel/ppc_ksyms.c b/arch/powerpc/kernel/ppc_ksyms.c
index 41e1607..ef7024da 100644
--- a/arch/powerpc/kernel/ppc_ksyms.c
+++ b/arch/powerpc/kernel/ppc_ksyms.c
@@ -28,10 +28,6 @@ EXPORT_SYMBOL(load_vr_state);
 EXPORT_SYMBOL(store_vr_state);
 #endif
 
-#ifdef CONFIG_VSX
-EXPORT_SYMBOL_GPL(__giveup_vsx);
-#endif
-
 #ifdef CONFIG_EPAPR_PARAVIRT
 EXPORT_SYMBOL(epapr_hypercall_start);
 #endif
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 5566c32..3d907b8 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -252,20 +252,33 @@ EXPORT_SYMBOL_GPL(flush_altivec_to_thread);
 #endif /* CONFIG_ALTIVEC */
 
 #ifdef CONFIG_VSX
-void giveup_vsx(struct task_struct *tsk)
+void __giveup_vsx(struct task_struct *tsk)
 {
-	check_if_tm_restore_required(tsk);
-
-	msr_check_and_set(MSR_FP|MSR_VEC|MSR_VSX);
 	if (tsk->thread.regs->msr & MSR_FP)
 		__giveup_fpu(tsk);
 	if (tsk->thread.regs->msr & MSR_VEC)
 		__giveup_altivec(tsk);
+	tsk->thread.regs->msr &= ~MSR_VSX;
+}
+
+void giveup_vsx(struct task_struct *tsk)
+{
+	check_if_tm_restore_required(tsk);
+
+	msr_check_and_set(MSR_FP|MSR_VEC|MSR_VSX);
 	__giveup_vsx(tsk);
 	msr_check_and_clear(MSR_FP|MSR_VEC|MSR_VSX);
 }
 EXPORT_SYMBOL(giveup_vsx);
 
+void save_vsx(struct task_struct *tsk)
+{
+	if (tsk->thread.regs->msr & MSR_FP)
+		save_fpu(tsk);
+	if (tsk->thread.regs->msr & MSR_VEC)
+		save_altivec(tsk);
+}
+
 void enable_kernel_vsx(void)
 {
 	WARN_ON(preemptible());
@@ -465,7 +478,7 @@ void save_all(struct task_struct *tsk)
 #endif
 #ifdef CONFIG_VSX
 	if (usermsr & MSR_VSX)
-		__giveup_vsx(tsk);
+		save_vsx(tsk);
 #endif
 #ifdef CONFIG_SPE
 	if (usermsr & MSR_SPE)
diff --git a/arch/powerpc/kernel/vector.S b/arch/powerpc/kernel/vector.S
index 51b0c17..1c2e7a3 100644
--- a/arch/powerpc/kernel/vector.S
+++ b/arch/powerpc/kernel/vector.S
@@ -151,23 +151,6 @@ _GLOBAL(load_up_vsx)
 	std	r12,_MSR(r1)
 	b	fast_exception_return
 
-/*
- * __giveup_vsx(tsk)
- * Disable VSX for the task given as the argument.
- * Does NOT save vsx registers.
- */
-_GLOBAL(__giveup_vsx)
-	addi	r3,r3,THREAD		/* want THREAD of task */
-	ld	r5,PT_REGS(r3)
-	cmpdi	0,r5,0
-	beq	1f
-	ld	r4,_MSR-STACK_FRAME_OVERHEAD(r5)
-	lis	r3,MSR_VSX@h
-	andc	r4,r4,r3		/* disable VSX for previous task */
-	std	r4,_MSR-STACK_FRAME_OVERHEAD(r5)
-1:
-	blr
-
 #endif /* CONFIG_VSX */

-- 
2.7.0