[PATCH v2] powerpc32: memcpy/memset: only use dcbz once cache is enabled
mpe at ellerman.id.au
Mon Sep 14 19:59:10 AEST 2015
On Sat, 2015-09-12 at 11:57 +0200, christophe leroy wrote:
> Le 11/09/2015 03:24, Michael Ellerman a écrit :
> > On Thu, 2015-09-10 at 17:05 -0500, Scott Wood wrote:
> >> 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.
> I've just thought about maybe another alternative.
> Is there any issue with calling do_feature_fixups() twice for the same
> features ?
Not that I can think of, but you never know.
> If not, we could define a MMU_CACHE_NOW_ON dummy MMU feature, then
> call again do_feature_fixups() in machine_init() to patch memcpy/memset
> stuff, something like:
> In arch/powerpc/include/asm/mmu.h:
> +#define MMU_CACHE_NOW_ON ASM_CONST(0x00008000)
> In arch/powerpc/kernel/setup_32.c: @machine_init()
> + spec = identify_cpu(0, mfspr(SPRN_PVR));
> + do_feature_fixups(spec->mmu_features | MMU_CACHE_NOW_ON,
> + &__start___mmu_ftr_fixup,
> + &__stop___mmu_ftr_fixup);
Did you try that? It would be cleaner, especially now that you have to do memset as well.
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