arm64: proc: Set PTE_NG for table entries to avoid traversing them twice

When KASAN is enabled, the swapper page table contains many identical
mappings of the zero page, which can lead to a stall during boot whilst
the G -> nG code continually walks the same page table entries looking
for global mappings.

This patch sets the nG bit (bit 11, which is IGNORED) in table entries
after processing the subtree so we can easily skip them if we see them
a second time.

Change-Id: Ifaf72c402ff9f0ac7100e573eba7134fd338eb52
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-commit: 2ce77f6d8a9ae9ce6d80397d88bdceb84a2004cd
Git-Repo: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/


Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>