Re: [PATCH 3/5] arm64: mm: use a compile time constant for vabits_actual when possible

The size of the kernel VA space is a compile time constant unless the
kernel is built to support 52-bit virtual addressing, which today is
only supported on 64k page size kernels (although this has recently
changed in the architecture).

This means that in many configurations, vabits_actual can never deviate
from its build time default, making it rather pointless to carry this
value in a variable. So use a compile time constant for vabits_actual
unless it can really assume different values.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/memory.h |  4 ++++
 arch/arm64/kernel/head.S        | 12 ++++++------
 arch/arm64/mm/mmu.c             |  2 ++
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index c759faf7a1ff..501c5c87ec0a 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h

@@ -179,7 +179,11 @@
 #include <linux/types.h>
 #include <asm/bug.h>
 
+#ifdef CONFIG_ARM64_VA_BITS_52
 extern u64			vabits_actual;
+#else
+#define vabits_actual		((u64)VA_BITS)
+#endif