net: thunder: change q_len's type to handle max ring size
sunil.kovvuri at gmail.com
Thu Feb 8 20:29:52 PST 2018
On Fri, Feb 9, 2018 at 3:27 AM, Dean Nelson <dnelson at redhat.com> wrote:
> On 02/08/2018 02:34 PM, David Miller wrote:
>> From: Dean Nelson <dnelson at redhat.com>
>>> The Cavium thunder nicvf driver supports rx/tx rings of up to 65536
>>> entries per.
>>> The number of entires are stored in the q_len member of struct
>>> q_desc_mem. The
>>> problem is that q_len being a u16, results in 65536 becoming 0.
>>> In getting pointers to descriptors in the rings, the driver uses q_len
>>> minus 1
>>> as a mask after incrementing the pointer, in order to go back to the
>>> and not go past the end of the ring.
>>> With the q_len set to 0 the mask is no longer correct and the driver does
>>> beyond the end of the ring, causing various ills. Usually the first thing
>>> shows up is a "NETDEV WATCHDOG: enP2p1s0f1 (nicvf): transmit queue 7
>>> timed out"
>>> This patch remedies the problem by changing q_len to a u32.
>>> Signed-off-by: Dean Nelson <dnelson at redhat.com>
>> Applied, thanks.
> Thank you!
>> Another way to solve this could have been to encode that length
>> as "length - 1"
> True. I had pondered that, but felt that since changing q_len's type
> didn't add any length to the structure and that it was less impactful
> from a number-of-lines of code changed perspective, I'd opt for this
> Cavium, if you'd prefer this goes the route that Dave just mentioned,
> please let me know and I can make a new patch against what's been
Thanks for fixing this and i think the current patch is fine.
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