On 05/13/2013 02:40 PM, Eric Dumazet wrote:
On Mon, 2013-05-13 at 14:34 -0700, Nithin Nayak Sujir wrote:
On 05/13/2013 02:14 PM, Eric Dumazet wrote:
+/* Test for TSO DMA buffers that cross into regions which are within MSS bytes
+ * of any 4GB boundaries: 4G, 8G, etc
+ */
+static inline int tg3_4g_tso_overflow_test(struct tg3 *tp, dma_addr_t mapping,
+ u32 len, u32 mss)
+{
+ if (tg3_asic_rev(tp) == ASIC_REV_5762 && mss) {
+ u32 base = (u32) mapping & 0xffffffff;
+
+ return ((base + len + (mss & 0x3fff)) < base);
+ }
+ return 0;
+}
+
I am curious : Does this condition even triggers ?
Yes, it's a rare problem to occur and was reported in our lab. After we
implemented this fix, the problem didn't happen again.
I just cant figure out which part of the kernel could allocate a
fragment spanning a 4G region.
For the bug to occur, the fragment does not have to span a 4G boundary. If it is
within MSS bytes (9.6k) of a 4G boundary, it triggers the failure.
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