powerpc: Add the ability to save Altivec without giving it up

This patch adds the ability to be able to save the VEC 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 registers in the
thread copy path to avoid a possibly pointless reload of VEC state.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index 6a201e8dc94791dc4c5b6dca6c7bb9f194fcf818..9028822bb73f52c25c75ea4571942b7bebc9d10e 100644 (file)
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -43,12 +43,13 @@ static inline void flush_fp_to_thread(struct task_struct *t) { }
 extern void enable_kernel_altivec(void);
 extern void flush_altivec_to_thread(struct task_struct *);
 extern void giveup_altivec(struct task_struct *);
-extern void __giveup_altivec(struct task_struct *);
+extern void save_altivec(struct task_struct *);
 static inline void disable_kernel_altivec(void)
 {
        msr_check_and_clear(MSR_VEC);
 }
 #else
+static inline void save_altivec(struct task_struct *t) { }
 static inline void __giveup_altivec(struct task_struct *t) { }
 #endif
 

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index a7e5061187e890100e1d461db707c858d5ae4dea..14c09d25de98b68df8738286ed9469299f364a00 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -213,6 +213,16 @@ static int restore_fp(struct task_struct *tsk) { return 0; }
 #ifdef CONFIG_ALTIVEC
 #define loadvec(thr) ((thr).load_vec)
 
+static void __giveup_altivec(struct task_struct *tsk)
+{
+       save_altivec(tsk);
+       tsk->thread.regs->msr &= ~MSR_VEC;
+#ifdef CONFIG_VSX
+       if (cpu_has_feature(CPU_FTR_VSX))
+               tsk->thread.regs->msr &= ~MSR_VSX;
+#endif
+}
+
 void giveup_altivec(struct task_struct *tsk)
 {
        check_if_tm_restore_required(tsk);
@@ -472,7 +482,7 @@ void save_all(struct task_struct *tsk)
                save_fpu(tsk);
 
        if (usermsr & MSR_VEC)
-               __giveup_altivec(tsk);
+               save_altivec(tsk);
 
        if (usermsr & MSR_VSX)
                __giveup_vsx(tsk);

diff --git a/arch/powerpc/kernel/vector.S b/arch/powerpc/kernel/vector.S
index 038cff8cf5f2473047945fb2fb584d7ed850bf8b..51b0c175ea8ce400a5fb7cbf6d103e9e3f41fdb6 100644 (file)
--- a/arch/powerpc/kernel/vector.S
+++ b/arch/powerpc/kernel/vector.S
@@ -106,36 +106,20 @@ _GLOBAL(load_up_altivec)
        blr
 
 /*
- * __giveup_altivec(tsk)
- * Disable VMX for the task given as the argument,
- * and save the vector registers in its thread_struct.
+ * save_altivec(tsk)
+ * Save the vector registers to its thread_struct
  */
-_GLOBAL(__giveup_altivec)
+_GLOBAL(save_altivec)
        addi    r3,r3,THREAD            /* want THREAD of task */
        PPC_LL  r7,THREAD_VRSAVEAREA(r3)
        PPC_LL  r5,PT_REGS(r3)
        PPC_LCMPI       0,r7,0
        bne     2f
        addi    r7,r3,THREAD_VRSTATE
-2:     PPC_LCMPI       0,r5,0
-       SAVE_32VRS(0,r4,r7)
+2:     SAVE_32VRS(0,r4,r7)
        mfvscr  v0
        li      r4,VRSTATE_VSCR
        stvx    v0,r4,r7
-       beq     1f
-       PPC_LL  r4,_MSR-STACK_FRAME_OVERHEAD(r5)
-#ifdef CONFIG_VSX
-BEGIN_FTR_SECTION
-       lis     r3,(MSR_VEC|MSR_VSX)@h
-FTR_SECTION_ELSE
-       lis     r3,MSR_VEC@h
-ALT_FTR_SECTION_END_IFSET(CPU_FTR_VSX)
-#else
-       lis     r3,MSR_VEC@h
-#endif
-       andc    r4,r4,r3                /* disable FP for previous task */
-       PPC_STL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
-1:
        blr
 
 #ifdef CONFIG_VSX