powerpc: Prepare for splitting giveup_{fpu, altivec, vsx} in two

This prepares for the decoupling of saving {fpu,altivec,vsx} registers and
marking {fpu,altivec,vsx} as being unused by a thread.

Currently giveup_{fpu,altivec,vsx}() does both however optimisations to
task switching can be made if these two operations are decoupled.
save_all() will permit the saving of registers to thread structs and leave
threads MSR with bits enabled.

This patch introduces no functional change.

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

1 files changed, 30 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 55c1eb0465af..29da07fb3b4a 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -444,12 +444,41 @@ 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);
+
+        if (usermsr & MSR_FP)
+                __giveup_fpu(tsk);
+
+        if (usermsr & MSR_VEC)
+                __giveup_altivec(tsk);
+
+        if (usermsr & MSR_VSX)
+                __giveup_vsx(tsk);
+
+        if (usermsr & MSR_SPE)
+                __giveup_spe(tsk);
+
+        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)