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SubjectRe: [PATCH 09/11] powerpc/8xx: dont save CR in SCRATCH registers

Le 05/01/2015 19:30, Joakim Tjernlund a écrit :
> On Tue, 2014-12-16 at 16:03 +0100, Christophe Leroy wrote:
>> CR only needs to be preserved when checking if we are handling a kernel address.
>> So we can preserve CR in a register:
>> - In ITLBMiss, check is done only when CONFIG_MODULES is defined. Otherwise we
>> don't need to do anything at all with CR.
>> - If CONFIG_8xx_CPU6 is defined, we have r3 available for saving CR
>> - Otherwise, we use r10, then we reload SRR0/MD_EPN into r10 when CR is restored
> I think the #ifdef CPU6 code makes for too much maintenance. Can you
> loose the #ifdef CPU6 and adjust code so it works for both cases?
I wanted to take the opportunity to save one cycle, but we are wasting
so many cycles with CPU6 that it is propably not worth it.
Ok, I will remove the special handling for CPU6.

>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>>
>> ---
>> arch/powerpc/kernel/head_8xx.S | 53 +++++++++++++++++++++++++++++-------------
>> 1 file changed, 37 insertions(+), 16 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
>> index c89aed9..a073918 100644
>> --- a/arch/powerpc/kernel/head_8xx.S
>> +++ b/arch/powerpc/kernel/head_8xx.S
>> @@ -308,14 +308,10 @@ SystemCall:
>> #endif
>>
>> InstructionTLBMiss:
>> + EXCEPTION_PROLOG_0
>> #ifdef CONFIG_8xx_CPU6
>> mtspr SPRN_DAR, r3
>> #endif
>> - EXCEPTION_PROLOG_0
>> - mfcr r10
>> - mtspr SPRN_SPRG_SCRATCH2, r10
>> - mfspr r10, SPRN_SRR0/* Get effective address of fault */
>> - DO_8xx_CPU15(r11, r10)
>>
>> /* If we are faulting a kernel address, we have to use the
>> * kernel page tables.
>> @@ -323,14 +319,33 @@ InstructionTLBMiss:
>> #ifdef CONFIG_MODULES
>> /* Only modules will cause ITLB Misses as we always
>> * pin the first 8MB of kernel memory */
>> +#ifdef CONFIG_8xx_CPU6
>> + mfspr r10, SPRN_SRR0/* Get effective address of fault */
>> + DO_8xx_CPU15(r11, r10)
>> + mfcr r3
>> andis. r11, r10, 0x8000/* Address >= 0x80000000 */
>> +#else
>> + mfspr r11, SPRN_SRR0/* Get effective address of fault */
>> + DO_8xx_CPU15(r10, r11)
>> + mfcr r10
>> + andis. r11, r11, 0x8000/* Address >= 0x80000000 */
>> #endif
>> mfspr r11, SPRN_M_TW/* Get level 1 table base address */
>> -#ifdef CONFIG_MODULES
>> beq 3f
>> lis r11, (swapper_pg_dir-PAGE_OFFSET)@ha
>> 3:
>> +#ifdef CONFIG_8xx_CPU6
>> + mtcr r3
>> +#else
>> + mtcr r10
>> + mfspr r10, SPRN_SRR0/* Get effective address of fault */
>> #endif
>> +#else /* CONFIG_MODULES */
>> + mfspr r10, SPRN_SRR0/* Get effective address of fault */
>> + DO_8xx_CPU15(r11, r10)
>> + mfspr r11, SPRN_M_TW/* Get level 1 table base address */
>> +#endif /* CONFIG_MODULES */
>> +
>> /* Insert level 1 index */
>> rlwimi r11, r10, 32 - ((PAGE_SHIFT - 2) << 1), (PAGE_SHIFT - 2) << 1, 29
>> lwz r11, (swapper_pg_dir-PAGE_OFFSET)@l(r11)/* Get the level 1 entry */
>> @@ -362,29 +377,37 @@ InstructionTLBMiss:
>> mfspr r3, SPRN_DAR
>> mtspr SPRN_DAR, r11/* Tag DAR */
>> #endif
>> - mfspr r10, SPRN_SPRG_SCRATCH2
>> - mtcr r10
>> EXCEPTION_EPILOG_0
>> rfi
>>
>> . = 0x1200
>> DataStoreTLBMiss:
>> -#ifdef CONFIG_8xx_CPU6
>> - mtspr SPRN_DAR, r3
>> -#endif
>> EXCEPTION_PROLOG_0
>> - mfcr r10
>> - mtspr SPRN_SPRG_SCRATCH2, r10
>> - mfspr r10, SPRN_MD_EPN
>>
>> /* If we are faulting a kernel address, we have to use the
>> * kernel page tables.
>> */
>> +#ifdef CONFIG_8xx_CPU6
>> + mtspr SPRN_DAR, r3
>> + mfcr r3
>> + mfspr r10, SPRN_MD_EPN
>> andis. r11, r10, 0x8000
>> +#else
>> + mfcr r10
>> + mfspr r11, SPRN_MD_EPN
>> + andis. r11, r11, 0x8000
>> +#endif
>> mfspr r11, SPRN_M_TW/* Get level 1 table base address */
>> beq 3f
>> lis r11, (swapper_pg_dir-PAGE_OFFSET)@ha
>> 3:
>> +#ifdef CONFIG_8xx_CPU6
>> + mtcr r3
>> +#else
>> + mtcr r10
>> + mfspr r10, SPRN_MD_EPN
>> +#endif
>> +
>> /* Insert level 1 index */
>> rlwimi r11, r10, 32 - ((PAGE_SHIFT - 2) << 1), (PAGE_SHIFT - 2) << 1, 29
>> lwz r11, (swapper_pg_dir-PAGE_OFFSET)@l(r11)/* Get the level 1 entry */
>> @@ -441,8 +464,6 @@ DataStoreTLBMiss:
>> mfspr r3, SPRN_DAR
>> #endif
>> mtspr SPRN_DAR, r11/* Tag DAR */
>> - mfspr r10, SPRN_SPRG_SCRATCH2
>> - mtcr r10
>> EXCEPTION_EPILOG_0
>> rfi
>>



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