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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>
This commit is contained in:
Ard Biesheuvel 2018-11-07 18:10:38 +01:00 committed by Catalin Marinas
parent 313a06e636
commit 26a4676faa
1 changed files with 8 additions and 0 deletions
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8
arch/arm64/include/asm/processor.h
View File

@ -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__