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Groups > linux.kernel > #1222467
| From | Michael Ellerman <mpe@ellerman.id.au> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled |
| Date | 2015-09-11 03:30 +0200 |
| Message-ID | <q7lk5-2Q0-3@gated-at.bofh.it> (permalink) |
| References | <q73Qe-2gG-9@gated-at.bofh.it> <q7icx-6iX-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, 2015-09-10 at 17:05 -0500, Scott Wood wrote:
> On Thu, 2015-09-10 at 08:41 +0200, Christophe Leroy wrote:
> >
> > +/* Cache related sections */
> > +#define BEGIN_CACHE_SECTION_NESTED(label) START_FTR_SECTION(label)
> > +#define BEGIN_CACHE_SECTION START_FTR_SECTION(97)
> > +
> > +#define END_CACHE_SECTION_NESTED(msk, val, label) \
> > + FTR_SECTION_ELSE_NESTED(label) \
> > + MAKE_FTR_SECTION_ENTRY(msk, val, label, __cache_fixup)
> > +
> > +#define END_CACHE_SECTION(msk, val) \
> > + END_CACHE_SECTION_NESTED(msk, val, 97)
> > +
> > +#define END_CACHE_SECTION_IFSET(msk) END_CACHE_SECTION((msk), (msk))
> > +#define END_CACHE_SECTION_IFCLR(msk) END_CACHE_SECTION((msk), 0)
> > +
> > +/* CACHE feature sections with alternatives, use BEGIN_FTR_SECTION to
> > start */
> > +#define CACHE_SECTION_ELSE_NESTED(label) FTR_SECTION_ELSE_NESTED(label)
> > +#define CACHE_SECTION_ELSE CACHE_SECTION_ELSE_NESTED(97)
> > +#define ALT_CACHE_SECTION_END_NESTED(msk, val, label) \
> > + MAKE_FTR_SECTION_ENTRY(msk, val, label, __cache_fixup)
> > +#define ALT_CACHE_SECTION_END_NESTED_IFSET(msk, label) \
> > + ALT_CACHE_SECTION_END_NESTED(msk, msk, label)
> > +#define ALT_CACHE_SECTION_END_NESTED_IFCLR(msk, label) \
> > + ALT_CACHE_SECTION_END_NESTED(msk, 0, label)
> > +#define ALT_CACHE_SECTION_END(msk, val) \
> > + ALT_CACHE_SECTION_END_NESTED(msk, val, 97)
> > +#define ALT_CACHE_SECTION_END_IFSET(msk) \
> > + ALT_CACHE_SECTION_END_NESTED_IFSET(msk, 97)
> > +#define ALT_CACHE_SECTION_END_IFCLR(msk) \
> > + ALT_CACHE_SECTION_END_NESTED_IFCLR(msk, 97)
>
> I don't think this duplication is what Michael meant by "the normal cpu
> feature sections". What else is going to use this very specific
> infrastructure?
Yeah, sorry, I was hoping you could do it with the existing cpu feature
mechanism.
It looks like the timing doesn't work, ie. you need to patch this stuff in
machine_init(), which is later than the regular patching which gets done in
early_init().
This is one of the festering differences we have between the 32 and 64-bit
initialisation code, ie. on 64-bit we do the patching much later.
So I think the cleanest solution is to have memcpy branch to generic_memcpy by
default, and then patch that to a nop once you're up and running. Something
like:
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index bb02e9f6944e..1c1a4e8866ad 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -38,6 +38,7 @@
#include <asm/udbg.h>
#include <asm/mmu_context.h>
#include <asm/epapr_hcalls.h>
+#include <asm/code-patching.h>
#define DBG(fmt...)
@@ -119,6 +120,8 @@ notrace void __init machine_init(u64 dt_ptr)
/* Do some early initialization based on the flat device tree */
early_init_devtree(__va(dt_ptr));
+ patch_instruction((unsigned int *)&memcpy, 0x60000000);
+
epapr_paravirt_early_init();
early_init_mmu();
diff --git a/arch/powerpc/lib/copy_32.S b/arch/powerpc/lib/copy_32.S
index 2ef50c629470..6446d2915e41 100644
--- a/arch/powerpc/lib/copy_32.S
+++ b/arch/powerpc/lib/copy_32.S
@@ -135,6 +135,7 @@ _GLOBAL(memmove)
/* fall through */
_GLOBAL(memcpy)
+ b generic_memcpy
add r7,r3,r5 /* test if the src & dst overlap */
add r8,r4,r5
cmplw 0,r4,r7
cheers
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[PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled Christophe Leroy <christophe.leroy@c-s.fr> - 2015-09-10 08:50 +0200
Re: [PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled Scott Wood <scottwood@freescale.com> - 2015-09-11 00:10 +0200
Re: [PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled Michael Ellerman <mpe@ellerman.id.au> - 2015-09-11 03:30 +0200
Re: [PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled christophe leroy <christophe.leroy@c-s.fr> - 2015-09-12 12:00 +0200
Re: [PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled Michael Ellerman <mpe@ellerman.id.au> - 2015-09-14 12:00 +0200
Re: [PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled Scott Wood <scottwood@freescale.com> - 2015-09-14 18:40 +0200
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