From: "Aneesh Kumar K.V" <aneesh.kumar@linux•vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel•crashing.org>,
Balbir Singh <bsingharora@gmail•com>,
paulus@samba•org, mpe@ellerman•id.au
Cc: linuxppc-dev@lists•ozlabs.org
Subject: Re: [PATCH] powerpc/mm: Use jump label to speed up radix_enabled check
Date: Wed, 27 Apr 2016 15:00:03 +0530 [thread overview]
Message-ID: <87k2jje6w4.fsf@skywalker.in.ibm.com> (raw)
In-Reply-To: <87mvofedtd.fsf@skywalker.in.ibm.com>
"Aneesh Kumar K.V" <aneesh.kumar@linux•vnet.ibm.com> writes:
> Benjamin Herrenschmidt <benh@kernel•crashing.org> writes:
>
>> On Wed, 2016-04-27 at 11:00 +1000, Balbir Singh wrote:
>>> Just basic testing across CPUs with various mm features=C2=A0
>>> enabled/disabled. Just for sanity
>>
>> I still don't think it's worth scattering the change. Either the jump
>> label works or it doesn't ... The only problem is make sure we identify
>> all the pre-boot ones but that's about it.
>>
>
> There are two ways to do this. One is to follow the approach listed
> below done by Kevin, which is to do the jump_label_init early during boot=
and
> switch both cpu and mmu feature check to plain jump label.
>
> http://mid.gmane.org/1440415228-8006-1-git-send-email-haokexin@gmail.com
>
> I already found one use case of cpu_has_feature before that
> jump_label_init. In this approach we need to carefully audit all the
> cpu/mmu_has_feature calls to make sure they don't get called before
> jump_label_init. A missed conversion mean we miss a cpu/mmu feature
> check.
>
>
> Other option is to follow the patch I posted above, with the simple
> change of renaming mmu_feature_enabled to mmu_has_feature. So we can
> use it in early boot without really worrying about when we init jump
> label.
>
> What do you suggest we follow ?
>
Something simple as below ?
diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/includ=
e/asm/book3s/64/mmu.h
index 696b7c5cc31f..0835a8f9904b 100644
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -23,7 +23,7 @@ struct mmu_psize_def {
};
extern struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT];
=20
-#define radix_enabled() mmu_feature_enabled(MMU_FTR_RADIX)
+#define radix_enabled() mmu_has_feature(MMU_FTR_RADIX)
=20
#endif /* __ASSEMBLY__ */
=20
diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
index fdb70dc218e5..d4b726f5bd4a 100644
--- a/arch/powerpc/include/asm/mmu.h
+++ b/arch/powerpc/include/asm/mmu.h
@@ -115,7 +115,7 @@
DECLARE_PER_CPU(int, next_tlbcam_idx);
#endif
=20
-static inline int mmu_has_feature(unsigned long feature)
+static inline int __mmu_has_feature(unsigned long feature)
{
return (cur_cpu_spec->mmu_features & feature);
}
@@ -145,7 +145,7 @@ static inline void assert_pte_locked(struct mm_struct *=
mm, unsigned long addr)
#endif /* !CONFIG_DEBUG_VM */
=20
#ifdef HAVE_JUMP_LABEL
-static __always_inline bool mmu_feature_enabled(unsigned long feature)
+static __always_inline bool mmu_has_feature(unsigned long feature)
{
asm_volatile_goto("1:\n\t"
".pushsection __mmu_ftr_fixup_c, \"a\"\n\t"
@@ -155,7 +155,7 @@ static __always_inline bool mmu_feature_enabled(unsigne=
d long feature)
JUMP_ENTRY_TYPE "%l[l_false]\n\t"
".popsection\n\t"
: : "i"(feature) : : l_true, l_false);
- if (mmu_has_feature(feature))
+ if (__mmu_has_feature(feature))
l_true:
return true;
l_false:
next prev parent reply other threads:[~2016-04-27 9:30 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-26 16:24 [PATCH] powerpc/mm: Use jump label to speed up radix_enabled check Aneesh Kumar K.V
2016-04-26 21:05 ` Benjamin Herrenschmidt
2016-04-26 22:16 ` Balbir Singh
2016-04-26 23:05 ` Benjamin Herrenschmidt
2016-04-27 1:00 ` Balbir Singh
2016-04-27 1:46 ` Benjamin Herrenschmidt
2016-04-27 7:00 ` Aneesh Kumar K.V
2016-04-27 9:30 ` Aneesh Kumar K.V [this message]
2016-06-09 4:12 ` Benjamin Herrenschmidt
2016-06-09 6:00 ` Aneesh Kumar K.V
2016-06-09 15:58 ` Aneesh Kumar K.V
2016-06-10 4:16 ` Michael Ellerman
2016-06-10 5:46 ` Benjamin Herrenschmidt
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