Commit 5acbbd42 authored Mar 30, 2010 by FUJITA Tomonori Committed by David S. Miller Apr 01, 2010

net: change illegal_highdma to use dma_mask

Robert Hancock pointed out two problems about NETIF_F_HIGHDMA:

-Many drivers only set the flag when they detect they can use 64-bit DMA,
since otherwise they could receive DMA addresses that they can't handle
(which on platforms without IOMMU/SWIOTLB support is fatal). This means that if
64-bit support isn't available, even buffers located below 4GB will get copied
unnecessarily.

-Some drivers set the flag even though they can't actually handle 64-bit DMA,
which would mean that on platforms without IOMMU/SWIOTLB they would get a DMA
mapping error if the memory they received happened to be located above 4GB.

http://lkml.org/lkml/2010/3/3/530



We can use the dma_mask if we need bouncing or not here. Then we can
safely fix drivers that misuse NETIF_F_HIGHDMA.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 4fd89b7a

net/core/dev.c

+14 −6

Original line number	Diff line number	Diff line
		@@ -129,6 +129,7 @@
		#include <linux/jhash.h>
		#include <linux/random.h>
		#include <trace/events/napi.h>
		#include <linux/pci.h>

		#include "net-sysfs.h"

		@@ -1804,14 +1805,21 @@ static inline int illegal_highdma(struct net_device dev, struct sk_buff skb)
		{
		#ifdef CONFIG_HIGHMEM
		int i;

		if (dev->features & NETIF_F_HIGHDMA)
		return 0;

		if (!(dev->features & NETIF_F_HIGHDMA)) {
		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
		if (PageHighMem(skb_shinfo(skb)->frags[i].page))
		return 1;
		}

		if (PCI_DMA_BUS_IS_PHYS) {
		struct device *pdev = dev->dev.parent;

		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		dma_addr_t addr = page_to_phys(skb_shinfo(skb)->frags[i].page);
		if (!pdev->dma_mask \|\| addr + PAGE_SIZE - 1 > *pdev->dma_mask)
		return 1;
		}
		}
		#endif
		return 0;
		}