Commit 26a4676f authored Nov 07, 2018 by Ard Biesheuvel Committed by Catalin Marinas Nov 08, 2018

arm64: mm: define NET_IP_ALIGN to 0



On arm64, there is no need to add 2 bytes of padding to the start of
each network buffer just to make the IP header appear 32-bit aligned.

Since this might actually adversely affect DMA performance some
platforms, let's override NET_IP_ALIGN to 0 to get rid of this
padding.

Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Tested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 313a06e6

arch/arm64/include/asm/processor.h

+8 −0

Original line number	Diff line number	Diff line
		@@ -24,6 +24,14 @@
		#define KERNEL_DS UL(-1)
		#define USER_DS (TASK_SIZE_64 - 1)

		/*
		* On arm64 systems, unaligned accesses by the CPU are cheap, and so there is
		* no point in shifting all network buffers by 2 bytes just to make some IP
		* header fields appear aligned in memory, potentially sacrificing some DMA
		* performance on some platforms.
		*/
		#define NET_IP_ALIGN 0

		#ifndef __ASSEMBLY__
		#ifdef __KERNEL__

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