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Subject[RFC PATCH v1 11/41] powerpc/32: Use fast instruction to set MSR RI in exception prolog on 8xx
Date
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: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/kernel/head_32.h | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index ac6b391f1493..25ee6b26ef5a 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -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 */
--
2.25.0
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