arm64: mm: Don't invalidate FROM_DEVICE buffers at start of DMA transfer

stable inclusion
from stable-v5.10.125
commit 1a264b3a6940b2595dc6b51edf8b1d9a71963fc7
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6EY

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1a264b3a6940b2595dc6b51edf8b1d9a71963fc7

--------------------------------

commit c50f11c6 upstream.

Invalidating the buffer memory in arch_sync_dma_for_device() for
FROM_DEVICE transfers

When using the streaming DMA API to map a buffer prior to inbound
non-coherent DMA (i.e. DMA_FROM_DEVICE), we invalidate any dirty CPU
cachelines so that they will not be written back during the transfer and
corrupt the buffer contents written by the DMA. This, however, poses two
potential problems:

  (1) If the DMA transfer does not write to every byte in the buffer,
      then the unwritten bytes will contain stale data once the transfer
      has completed.

  (2) If the buffer has a virtual alias in userspace, then stale data
      may be visible via this alias during the period between performing
      the cache invalidation and the DMA writes landing in memory.

Address both of these issues by cleaning (aka writing-back) the dirty
lines in arch_sync_dma_for_device(DMA_FROM_DEVICE) instead of discarding
them using invalidation.

Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220606152150.GA31568@willie-the-truckSigned-off-by: NWill Deacon <will@kernel.org>
Reviewed-by: NArd Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220610151228.4562-2-will@kernel.orgSigned-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>

arch/arm64/mm/cache.S

@@ -228,8 +228,6 @@ SYM_FUNC_END_PI(__dma_flush_area)
  *	- dir	- DMA direction
  */
 SYM_FUNC_START_PI(__dma_map_area)
-	cmp	w2, #DMA_FROM_DEVICE
-	b.eq	__dma_inv_area
 	b	__dma_clean_area
 SYM_FUNC_END_PI(__dma_map_area)