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powerpc: Replace mfmsr instructions with load from PACA kernel_msr field

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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>
This commit is contained in:
Benjamin Herrenschmidt
2012-03-02 11:33:52 +11:00
parent 9424fabf86
commit d9ada91ae2
4 changed files with 10 additions and 15 deletions
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14
arch/powerpc/kernel/entry_64.S
View File

@@ -557,10 +557,8 @@ _GLOBAL(ret_from_except_lite)
#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 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
* 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 @@ do_work:
#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

5
arch/powerpc/kernel/exceptions-64s.S
View File

@@ -848,9 +848,8 @@ fast_exception_return:
REST_GPR(0, r1)
REST_8GPRS(2, r1)
mfmsr r10
rldicl r10,r10,48,1 /* clear EE */
rldicr r10,r10,16,61 /* clear RI (LE is 0 already) */
ld r10,PACAKMSR(r13)
clrrdi r10,r10,2 /* clear RI */
mtmsrd r10,1
mtspr SPRN_SRR1,r12