From: "Nithin Nayak Sujir" <nsujir@broadcom•com>
To: "Eric Dumazet" <eric.dumazet@gmail•com>
Cc: davem@davemloft•net, netdev@vger•kernel.org,
"Michael Chan" <mchan@broadcom•com>,
stable@vger•kernel.org
Subject: Re: [PATCH v2 net 2/2] tg3: Fix data corruption on 5725 with TSO
Date: Mon, 13 May 2013 14:47:35 -0700 [thread overview]
Message-ID: <51915F77.5000405@broadcom.com> (raw)
In-Reply-To: <1368481224.13473.124.camel@edumazet-glaptop>
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.
>
>
>
next prev parent reply other threads:[~2013-05-13 21:47 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-13 21:04 [PATCH v2 net 0/2] tg3: 2 bugfixes - TSO data corruption and phy power down Nithin Nayak Sujir
2013-05-13 21:04 ` [PATCH v2 net 1/2] tg3: Skip powering down function 0 on certain serdes devices Nithin Nayak Sujir
2013-05-14 18:08 ` Joe Perches
2013-05-14 18:17 ` Nithin Nayak Sujir
2013-05-13 21:04 ` [PATCH v2 net 2/2] tg3: Fix data corruption on 5725 with TSO Nithin Nayak Sujir
2013-05-13 21:14 ` Eric Dumazet
2013-05-13 21:34 ` Nithin Nayak Sujir
2013-05-13 21:40 ` Eric Dumazet
2013-05-13 21:47 ` Nithin Nayak Sujir [this message]
2013-05-13 22:10 ` Eric Dumazet
2013-05-14 8:40 ` David Laight
2013-05-14 15:04 ` Michael Chan
2013-05-14 15:20 ` David Laight
2013-05-14 16:19 ` Michael Chan
2013-05-14 16:46 ` Eric Dumazet
2013-05-15 8:56 ` David Laight
2013-05-15 15:12 ` Michael Chan
2013-05-15 15:23 ` Eric Dumazet
2013-05-15 15:51 ` Michael Chan
2013-05-14 18:32 ` [PATCH v2 net 0/2] tg3: 2 bugfixes - TSO data corruption and phy power down David Miller
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