ARM: DMA: ensure that old section mappings are flushed from the TLB

ARM: DMA: ensure that old section mappings are flushed from the TLB

commit 6b076991dca9817e75c37e2f0db6d52611ea42fa upstream.

When setting up the CMA region, we must ensure that the old section
mappings are flushed from the TLB before replacing them with page
tables, otherwise we can suffer from mismatched aliases if the CPU
speculatively prefetches from these mappings at an inopportune time.

A mismatched alias can occur when the TLB contains a section mapping,
but a subsequent prefetch causes it to load a page table mapping,
resulting in the possibility of the TLB containing two matching
mappings for the same virtual address region.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Hou Pengyang <houpengyang@huawei.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>