From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] powerpc/mm: Add mask of always present MMU features
Date: Wed, 21 Oct 2020 19:55:11 +0530 [thread overview]
Message-ID: <871rhrejw8.fsf@linux.ibm.com> (raw)
In-Reply-To: <4bc99005-f3c0-045b-e0d5-f8b6f2b2e90d@csgroup.eu>
Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 12/10/2020 à 17:39, Christophe Leroy a écrit :
>> On the same principle as commit 773edeadf672 ("powerpc/mm: Add mask
>> of possible MMU features"), add mask for MMU features that are
>> always there in order to optimise out dead branches.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>> v2: Features must be anded with MMU_FTRS_POSSIBLE instead of ~0, otherwise
>> MMU_FTRS_ALWAYS is ~0 when no #ifdef matches.
>
> This is still not enough. For BOOK3S/32, MMU_FTRS_POSSIBLE is still too much.
> We need a #ifdef CONFIG_PPC_BOOK3S_32 with 0.
>
> Christophe
>
>> ---
>> arch/powerpc/include/asm/mmu.h | 25 +++++++++++++++++++++++++
>> 1 file changed, 25 insertions(+)
>>
>> diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
>> index 255a1837e9f7..64e7e7f7cda9 100644
>> --- a/arch/powerpc/include/asm/mmu.h
>> +++ b/arch/powerpc/include/asm/mmu.h
>> @@ -201,8 +201,30 @@ enum {
>> 0,
>> };
>>
>> +enum {
>> + MMU_FTRS_ALWAYS =
>> +#ifdef CONFIG_PPC_8xx
>> + MMU_FTR_TYPE_8xx &
>> +#endif
>> +#ifdef CONFIG_40x
>> + MMU_FTR_TYPE_40x &
>> +#endif
>> +#ifdef CONFIG_PPC_47x
>> + MMU_FTR_TYPE_47x &
>> +#elif defined(CONFIG_44x)
>> + MMU_FTR_TYPE_44x &
>> +#endif
>> +#if defined(CONFIG_E200) || defined(CONFIG_E500)
>> + MMU_FTR_TYPE_FSL_E &
>> +#endif
>> + MMU_FTRS_POSSIBLE,
>> +};
Will it be simpler if we make it a #define like below?
#ifdef CONFIG_PPC_8XX
#define MMU_FTR_ALWAYS MMU_FTR_TYPE_8XX & MMU_FTR_POSSIBLE
#endif
>> +
>> static inline bool early_mmu_has_feature(unsigned long feature)
>> {
>> + if (MMU_FTRS_ALWAYS & feature)
>> + return true;
>> +
>> return !!(MMU_FTRS_POSSIBLE & cur_cpu_spec->mmu_features & feature);
>> }
>>
>> @@ -231,6 +253,9 @@ static __always_inline bool mmu_has_feature(unsigned long feature)
>> }
>> #endif
>>
>> + if (MMU_FTRS_ALWAYS & feature)
>> + return true;
>> +
>> if (!(MMU_FTRS_POSSIBLE & feature))
>> return false;
>>
>>
next prev parent reply other threads:[~2020-10-21 14:27 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-12 15:39 [PATCH v2] powerpc/mm: Add mask of always present MMU features Christophe Leroy
2020-10-21 10:32 ` Christophe Leroy
2020-10-21 14:25 ` Aneesh Kumar K.V [this message]
2020-10-21 16:37 ` Christophe Leroy
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