Commit 1fd6c022 authored by Michael Ellerman's avatar Michael Ellerman
Browse files

powerpc/mm: Add a CONFIG option to choose if radix is used by default 



Currently if the hardware supports the radix MMU we will use
it, *unless* "disable_radix" is passed on the kernel command line.

However some users would like the reverse semantics. ie. The kernel
uses the hash MMU by default, unless radix is explicitly requested on
the command line.

So add a CONFIG option to choose whether we use radix by default or
not, and expand the disable_radix command line option to allow
"disable_radix=no" which *enables* radix.

Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 4e003747

arch/powerpc/mm/init_64.c

+11 −2
Original line number Diff line number Diff line
@@ -368,10 +368,19 @@ EXPORT_SYMBOL_GPL(realmode_pfn_to_page); 
#endif /* CONFIG_SPARSEMEM_VMEMMAP */



#ifdef CONFIG_PPC_BOOK3S_64

static bool disable_radix;

static bool disable_radix = !IS_ENABLED(CONFIG_PPC_RADIX_MMU_DEFAULT);



static int __init parse_disable_radix(char *p)

{

	disable_radix = true;

	bool val;



	if (strlen(p) == 0)

		val = true;

	else if (kstrtobool(p, &val))

		return -EINVAL;



	disable_radix = val;



	return 0;

}

early_param("disable_radix", parse_disable_radix);

arch/powerpc/platforms/Kconfig.cputype

+13 −0
Original line number Diff line number Diff line
@@ -304,6 +304,19 @@ config PPC_RADIX_MMU 
	  is only implemented by IBM Power9 CPUs, if you don't have one of them

	  you can probably disable this.



config PPC_RADIX_MMU_DEFAULT

	bool "Default to using the Radix MMU when possible"

	depends on PPC_RADIX_MMU

	default y

	help

	  When the hardware supports the Radix MMU, default to using it unless

	  "disable_radix[=yes]" is specified on the kernel command line.



	  If this option is disabled, the Hash MMU will be used by default,

	  unless "disable_radix=no" is specified on the kernel command line.



	  If you're unsure, say Y.



config ARCH_ENABLE_HUGEPAGE_MIGRATION

	def_bool y

	depends on PPC_BOOK3S_64 && HUGETLB_PAGE && MIGRATION

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