powerpc: create giveup_all()

Create a single function that gives everything up (FP, VMX, VSX, SPE).
Doing this all at once means we only do one MSR write.

A context switch microbenchmark using yield():

http://ozlabs.org/~anton/junkcode/context_switch2.c

./context_switch2 --test=yield --fp --altivec --vector 0 0

shows an improvement of 3% on POWER8.

Signed-off-by: Anton Blanchard <anton@samba.org>
[mpe: giveup_all() needs to be EXPORT_SYMBOL'ed]
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 9414dcb..8f85678 100644 (file)
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -26,6 +26,7 @@ extern void __giveup_vsx(struct task_struct *);
 extern void giveup_vsx(struct task_struct *);
 extern void enable_kernel_spe(void);
 extern void load_up_spe(struct task_struct *);
+extern void giveup_all(struct task_struct *);
 extern void switch_booke_debug_regs(struct debug_reg *new_debug);
 
 #ifdef CONFIG_PPC_FPU

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 9f8444b..4c087b9 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -308,6 +308,65 @@ void flush_spe_to_thread(struct task_struct *tsk)
 }
 #endif /* CONFIG_SPE */
 
+static unsigned long msr_all_available;
+
+static int __init init_msr_all_available(void)
+{
+#ifdef CONFIG_PPC_FPU
+       msr_all_available |= MSR_FP;
+#endif
+#ifdef CONFIG_ALTIVEC
+       if (cpu_has_feature(CPU_FTR_ALTIVEC))
+               msr_all_available |= MSR_VEC;
+#endif
+#ifdef CONFIG_VSX
+       if (cpu_has_feature(CPU_FTR_VSX))
+               msr_all_available |= MSR_VSX;
+#endif
+#ifdef CONFIG_SPE
+       if (cpu_has_feature(CPU_FTR_SPE))
+               msr_all_available |= MSR_SPE;
+#endif
+
+       return 0;
+}
+early_initcall(init_msr_all_available);
+
+void giveup_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)
+               __giveup_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);
+}
+EXPORT_SYMBOL(giveup_all);
+
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
 void do_send_trap(struct pt_regs *regs, unsigned long address,
                  unsigned long error_code, int signal_code, int breakpt)
@@ -839,21 +898,8 @@ struct task_struct *__switch_to(struct task_struct *prev,
 
        __switch_to_tm(prev);
 
-       if (prev->thread.regs && (prev->thread.regs->msr & MSR_FP))
-               giveup_fpu(prev);
-#ifdef CONFIG_ALTIVEC
-       if (prev->thread.regs && (prev->thread.regs->msr & MSR_VEC))
-               giveup_altivec(prev);
-#endif /* CONFIG_ALTIVEC */
-#ifdef CONFIG_VSX
-       if (prev->thread.regs && (prev->thread.regs->msr & MSR_VSX))
-               /* VMX and FPU registers are already save here */
-               __giveup_vsx(prev);
-#endif /* CONFIG_VSX */
-#ifdef CONFIG_SPE
-       if ((prev->thread.regs && (prev->thread.regs->msr & MSR_SPE)))
-               giveup_spe(prev);
-#endif /* CONFIG_SPE */
+       /* Save FPU, Altivec, VSX and SPE state */
+       giveup_all(prev);
 
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
        switch_booke_debug_regs(&new->thread.debug);

diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 49f5dad..a78e0e6 100644 (file)
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -1490,21 +1490,8 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
                goto out;
        /* interrupts now hard-disabled */
 
-       /* Save FPU state in thread_struct */
-       if (current->thread.regs->msr & MSR_FP)
-               giveup_fpu(current);
-
-#ifdef CONFIG_ALTIVEC
-       /* Save Altivec state in thread_struct */
-       if (current->thread.regs->msr & MSR_VEC)
-               giveup_altivec(current);
-#endif
-
-#ifdef CONFIG_VSX
-       /* Save VSX state in thread_struct */
-       if (current->thread.regs->msr & MSR_VSX)
-               __giveup_vsx(current);
-#endif
+       /* Save FPU, Altivec and VSX state */
+       giveup_all(current);
 
        /* Preload FPU if it's enabled */
        if (kvmppc_get_msr(vcpu) & MSR_FP)