From 1461e3662292a9258e785c69fac14063359f00af Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 10 Jun 2022 16:12:27 +0100 Subject: [PATCH] arm64: mm: Don't invalidate FROM_DEVICE buffers at start of DMA transfer commit c50f11c6196f45c92ca48b16a5071615d4ae0572 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. Change-Id: Ibfda7d1f68d11d76c7b603f083d8ee773a37cc22 Cc: Ard Biesheuvel Cc: Christoph Hellwig Cc: Robin Murphy Cc: Russell King Cc: Link: https://lore.kernel.org/r/20220606152150.GA31568@willie-the-truck Signed-off-by: Will Deacon Reviewed-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20220610151228.4562-2-will@kernel.org Signed-off-by: Catalin Marinas Signed-off-by: Greg Kroah-Hartman Git-commit: 7b9c3bfbad2510478ac29221d2c40a09184ce6a1 Git-repo: https://android.googlesource.com/kernel/common/ Signed-off-by: Srinivasarao Pathipati --- arch/arm64/mm/cache.S | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S index 0ee30f93b546..a3ac18c2ec24 100644 --- a/arch/arm64/mm/cache.S +++ b/arch/arm64/mm/cache.S @@ -301,8 +301,6 @@ ENDPIPROC(__dma_flush_area) * - dir - DMA direction */ ENTRY(__dma_map_area) - cmp w2, #DMA_FROM_DEVICE - b.eq __dma_inv_area b __dma_clean_area ENDPIPROC(__dma_map_area)