arm64: mm: enable HAVE_RCU_TABLE_FREE logic

In order to implement fast_get_user_pages we need to ensure that the page
table walker is protected from page table pages being freed from under it.

This patch enables HAVE_RCU_TABLE_FREE, any page table pages belonging to
address spaces with multiple users will be call_rcu_sched freed.  Meaning
that disabling interrupts will block the free and protect the fast gup
page walker.

Signed-off-by: Steve Capper <steve.capper@linaro.org>
Tested-by: Dann Frazier <dann.frazier@canonical.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index e96cbe84d5ae..1ffd9a05206b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -57,6 +57,7 @@ config ARM64
         select HAVE_PERF_EVENTS
         select HAVE_PERF_REGS
         select HAVE_PERF_USER_STACK_DUMP
+        select HAVE_RCU_TABLE_FREE
         select HAVE_SYSCALL_TRACEPOINTS
         select IRQ_DOMAIN
         select MODULES_USE_ELF_RELA