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Commit c2085059 authored by Anton Blanchard's avatar Anton Blanchard Committed by Michael Ellerman
Browse files

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: default avatarAnton Blanchard <anton@samba.org>
[mpe: giveup_all() needs to be EXPORT_SYMBOL'ed]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 1f2e25b2

arch/powerpc/include/asm/switch_to.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kernel/process.c

+61 −15
Original line number Diff line number Diff line
@@ -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);

arch/powerpc/kvm/book3s_pr.c

+2 −15
Original line number Diff line number Diff line
@@ -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)