Commit b6254ced authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/signal: Don't manage floating point regs when no FPU 



There is no point in copying floating point regs when there
is no FPU and MATH_EMULATION is not selected.

Create a new CONFIG_PPC_FPU_REGS bool that is selected by
CONFIG_MATH_EMULATION and CONFIG_PPC_FPU, and use it to
opt out everything related to fp_state in thread_struct.

The asm const used only by fpu.S are opted out with CONFIG_PPC_FPU
as fpu.S build is conditionnal to CONFIG_PPC_FPU.

The following app spends approx 8.1 seconds system time on an 8xx
without the patch, and 7.0 seconds with the patch (13.5% reduction).

On an 832x, it spends approx 2.6 seconds system time without
the patch and 2.1 seconds with the patch (19% reduction).

	void sigusr1(int sig) { }

	int main(int argc, char **argv)
	{
		int i = 100000;

		signal(SIGUSR1, sigusr1);
		for (;i--;)
			raise(SIGUSR1);
		exit(0);
	}

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7569070083e6cd5b279bb5023da601aba3c06f3c.1597770847.git.christophe.leroy@csgroup.eu
parent 4d90eb97

arch/powerpc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -422,6 +422,7 @@ config HUGETLB_PAGE_SIZE_VARIABLE 
config MATH_EMULATION

	bool "Math emulation"

	depends on 4xx || PPC_8xx || PPC_MPC832x || BOOKE

	select PPC_FPU_REGS

	help

	  Some PowerPC chips designed for embedded applications do not have

	  a floating-point unit and therefore do not implement the

arch/powerpc/include/asm/processor.h

+2 −0
Original line number Diff line number Diff line
@@ -164,8 +164,10 @@ struct thread_struct { 
#endif

	/* Debug Registers */

	struct debug_reg debug;

#ifdef CONFIG_PPC_FPU_REGS

	struct thread_fp_state	fp_state;

	struct thread_fp_state	*fp_save_area;

#endif

	int		fpexc_mode;	/* floating-point exception mode */

	unsigned int	align_ctl;	/* alignment handling control */

#ifdef CONFIG_HAVE_HW_BREAKPOINT

arch/powerpc/kernel/asm-offsets.c

+2 −0
Original line number Diff line number Diff line
@@ -110,9 +110,11 @@ int main(void) 
#ifdef CONFIG_BOOKE

	OFFSET(THREAD_NORMSAVES, thread_struct, normsave[0]);

#endif

#ifdef CONFIG_PPC_FPU

	OFFSET(THREAD_FPEXC_MODE, thread_struct, fpexc_mode);

	OFFSET(THREAD_FPSTATE, thread_struct, fp_state.fpr);

	OFFSET(THREAD_FPSAVEAREA, thread_struct, fp_save_area);

#endif

	OFFSET(FPSTATE_FPSCR, thread_fp_state, fpscr);

	OFFSET(THREAD_LOAD_FP, thread_struct, load_fp);

#ifdef CONFIG_ALTIVEC

arch/powerpc/kernel/process.c

+4 −0
Original line number Diff line number Diff line
@@ -1730,7 +1730,9 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, 
		p->thread.ptrace_bps[i] = NULL;

#endif



#ifdef CONFIG_PPC_FPU_REGS

	p->thread.fp_save_area = NULL;

#endif

#ifdef CONFIG_ALTIVEC

	p->thread.vr_save_area = NULL;

#endif
@@ -1855,8 +1857,10 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp) 
#endif

	current->thread.load_slb = 0;

	current->thread.load_fp = 0;

#ifdef CONFIG_PPC_FPU_REGS

	memset(&current->thread.fp_state, 0, sizeof(current->thread.fp_state));

	current->thread.fp_save_area = NULL;

#endif

#ifdef CONFIG_ALTIVEC

	memset(&current->thread.vr_state, 0, sizeof(current->thread.vr_state));

	current->thread.vr_state.vscr.u[3] = 0x00010000; /* Java mode disabled */

arch/powerpc/kernel/ptrace/Makefile

+2 −2
Original line number Diff line number Diff line
@@ -6,11 +6,11 @@ 
CFLAGS_ptrace-view.o		+= -DUTS_MACHINE='"$(UTS_MACHINE)"'



obj-y				+= ptrace.o ptrace-view.o

obj-y				+= ptrace-fpu.o

obj-$(CONFIG_PPC_FPU_REGS)	+= ptrace-fpu.o

obj-$(CONFIG_COMPAT)		+= ptrace32.o

obj-$(CONFIG_VSX)		+= ptrace-vsx.o

ifneq ($(CONFIG_VSX),y)

obj-y				+= ptrace-novsx.o

obj-$(CONFIG_PPC_FPU_REGS)	+= ptrace-novsx.o

endif

obj-$(CONFIG_ALTIVEC)		+= ptrace-altivec.o

obj-$(CONFIG_SPE)		+= ptrace-spe.o