arm64: mm: ensure that the zero page is visible to the page table walker
commit 32d63978 upstream. In paging_init, we allocate the zero page, memset it to zero and then point TTBR0 to it in order to avoid speculative fetches through the identity mapping. In order to guarantee that the freshly zeroed page is indeed visible to the page table walker, we need to execute a dsb instruction prior to writing the TTBR. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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