Commit b0284cd2 authored by Catalin Marinas's avatar Catalin Marinas Committed by Marc Zyngier
Browse files

mm: Do not enable PG_arch_2 for all 64-bit architectures 



Commit 4beba948 ("mm: Add PG_arch_2 page flag") introduced a new
page flag for all 64-bit architectures. However, even if an architecture
is 64-bit, it may still have limited spare bits in the 'flags' member of
'struct page'. This may happen if an architecture enables SPARSEMEM
without SPARSEMEM_VMEMMAP as is the case with the newly added loongarch.
This architecture port needs 19 more bits for the sparsemem section
information and, while it is currently fine with PG_arch_2, adding any
more PG_arch_* flags will trigger build-time warnings.

Add a new CONFIG_ARCH_USES_PG_ARCH_X option which can be selected by
architectures that need more PG_arch_* flags beyond PG_arch_1. Select it
on arm64.

Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
[pcc@google.com: fix build with CONFIG_ARM64_MTE disabled]
Signed-off-by: default avatarPeter Collingbourne <pcc@google.com>
Reported-by: default avatarkernel test robot <lkp@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Steven Price <steven.price@arm.com>
Reviewed-by: default avatarSteven Price <steven.price@arm.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221104011041.290951-2-pcc@google.com
parent 30a0b95b

arch/arm64/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -1965,6 +1965,7 @@ config ARM64_MTE 
	depends on ARM64_PAN

	select ARCH_HAS_SUBPAGE_FAULTS

	select ARCH_USES_HIGH_VMA_FLAGS

	select ARCH_USES_PG_ARCH_X

	help

	  Memory Tagging (part of the ARMv8.5 Extensions) provides

	  architectural support for run-time, always-on detection of

fs/proc/page.c

+1 −1
Original line number Diff line number Diff line
@@ -219,7 +219,7 @@ u64 stable_page_flags(struct page *page) 
	u |= kpf_copy_bit(k, KPF_PRIVATE_2,	PG_private_2);

	u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE,	PG_owner_priv_1);

	u |= kpf_copy_bit(k, KPF_ARCH,		PG_arch_1);

#ifdef CONFIG_64BIT

#ifdef CONFIG_ARCH_USES_PG_ARCH_X

	u |= kpf_copy_bit(k, KPF_ARCH_2,	PG_arch_2);

#endif

include/linux/page-flags.h

+1 −1
Original line number Diff line number Diff line
@@ -132,7 +132,7 @@ enum pageflags { 
	PG_young,

	PG_idle,

#endif

#ifdef CONFIG_64BIT

#ifdef CONFIG_ARCH_USES_PG_ARCH_X

	PG_arch_2,

#endif

#ifdef CONFIG_KASAN_HW_TAGS

include/trace/events/mmflags.h

+4 −4
Original line number Diff line number Diff line
@@ -91,10 +91,10 @@ 
#define IF_HAVE_PG_IDLE(flag,string)

#endif



#ifdef CONFIG_64BIT

#define IF_HAVE_PG_ARCH_2(flag,string) ,{1UL << flag, string}

#ifdef CONFIG_ARCH_USES_PG_ARCH_X

#define IF_HAVE_PG_ARCH_X(flag,string) ,{1UL << flag, string}

#else

#define IF_HAVE_PG_ARCH_2(flag,string)

#define IF_HAVE_PG_ARCH_X(flag,string)

#endif



#ifdef CONFIG_KASAN_HW_TAGS
@@ -130,7 +130,7 @@ IF_HAVE_PG_UNCACHED(PG_uncached, "uncached" ) \ 
IF_HAVE_PG_HWPOISON(PG_hwpoison,	"hwpoison"	)		\

IF_HAVE_PG_IDLE(PG_young,		"young"		)		\

IF_HAVE_PG_IDLE(PG_idle,		"idle"		)		\

IF_HAVE_PG_ARCH_2(PG_arch_2,		"arch_2"	)		\

IF_HAVE_PG_ARCH_X(PG_arch_2,		"arch_2"	)		\

IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison")



#define show_page_flags(flags)						\

mm/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -1005,6 +1005,14 @@ config ARCH_USES_HIGH_VMA_FLAGS 
config ARCH_HAS_PKEYS

	bool



config ARCH_USES_PG_ARCH_X

	bool

	help

	  Enable the definition of PG_arch_x page flags with x > 1. Only

	  suitable for 64-bit architectures with CONFIG_FLATMEM or

	  CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be

	  enough room for additional bits in page->flags.



config VM_EVENT_COUNTERS

	default y

	bool "Enable VM event counters for /proc/vmstat" if EXPERT