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>

net/core/dev.c

@@ -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;
 }