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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2018-11-07 18:10:38 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2018-11-08 17:50:26 +0000
commit26a4676faa1ad5d99317e0cd701e5d6f3e716b77 (patch)
treee028f8b341426293dd78072515a6dac5a6c10fc2 /arch/arm64
parent313a06e636808387822af24c507cba92703568b1 (diff)
downloadlinux-26a4676faa1ad5d99317e0cd701e5d6f3e716b77.tar.bz2
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>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/include/asm/processor.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 3e2091708b8e..6b0d4dff5012 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -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__