powerpc: Replace mfmsr instructions with load from PACA kernel_msr field
On 64-bit, the mfmsr instruction can be quite slow, slower
than loading a field from the cache-hot PACA, which happens
to already contain the value we want in most cases.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index cc030b7..c513beb 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -557,10 +557,8 @@
#ifdef CONFIG_PPC_BOOK3E
wrteei 0
#else
- mfmsr r10 /* Get current interrupt state */
- rldicl r9,r10,48,1 /* clear MSR_EE */
- rotldi r9,r9,16
- mtmsrd r9,1 /* Update machine state */
+ ld r10,PACAKMSR(r13) /* Get kernel MSR without EE */
+ mtmsrd r10,1 /* Update machine state */
#endif /* CONFIG_PPC_BOOK3E */
#ifdef CONFIG_PREEMPT
@@ -625,8 +623,8 @@
* userspace and we take an exception after restoring r13,
* we end up corrupting the userspace r13 value.
*/
- mfmsr r4
- andc r4,r4,r0 /* r0 contains MSR_RI here */
+ ld r4,PACAKMSR(r13) /* Get kernel MSR without EE */
+ andc r4,r4,r0 /* r0 contains MSR_RI here */
mtmsrd r4,1
/*
@@ -686,9 +684,7 @@
#ifdef CONFIG_PPC_BOOK3E
wrteei 0
#else
- mfmsr r10
- rldicl r10,r10,48,1
- rotldi r10,r10,16
+ ld r10,PACAKMSR(r13) /* Get kernel MSR without EE */
mtmsrd r10,1
#endif /* CONFIG_PPC_BOOK3E */
li r0,0