Commit e464d92b authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/32: Use fast instruction to set MSR RI in exception prolog on 8xx 



8xx has registers SPRN_NRI, SPRN_EID and SPRN_EIE for changing
MSR EE and RI.

Use SPRN_EID in exception prolog to set RI.

On an 8xx, it reduces the null_syscall test by 3 cycles.

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/65f6bda827c2a2abce71ea7e07543e791163da33.1615552866.git.christophe.leroy@csgroup.eu
parent 79f4bb17

arch/powerpc/kernel/head_32.h

+2 −0
Original line number Diff line number Diff line
@@ -107,6 +107,8 @@ 
#endif

#ifdef CONFIG_40x

	rlwinm	r9,r9,0,14,12		/* clear MSR_WE (necessary?) */

#elif defined(CONFIG_PPC_8xx)

	mtspr	SPRN_EID, r2		/* Set MSR_RI */

#else

#ifdef CONFIG_VMAP_STACK

	li	r10, MSR_KERNEL & ~MSR_IR /* can take exceptions */