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 beginning
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 go
beyond the end of the ring, causing various ills. Usually the first thing that
shows up is a "NETDEV WATCHDOG: enP2p1s0f1 (nicvf): transmit queue 7 timed out"
warning.
This patch remedies the problem by changing q_len to a u32.
Signed-off-by: Dean Nelson <[email protected]>
---
drivers/net/ethernet/cavium/thunder/nicvf_queues.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_queues.h b/drivers/net/ethernet/cavium/thunder/nicvf_queues.h
index 7d1e4e2aaad0..ce1eed7a6d63 100644
--- a/drivers/net/ethernet/cavium/thunder/nicvf_queues.h
+++ b/drivers/net/ethernet/cavium/thunder/nicvf_queues.h
@@ -213,7 +213,7 @@ struct rx_tx_queue_stats {
struct q_desc_mem {
dma_addr_t dma;
u64 size;
- u16 q_len;
+ u32 q_len;
dma_addr_t phys_base;
void *base;
void *unalign_base;
From: Dean Nelson <[email protected]>
Date:
> 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 beginning
> 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 go
> beyond the end of the ring, causing various ills. Usually the first thing that
> shows up is a "NETDEV WATCHDOG: enP2p1s0f1 (nicvf): transmit queue 7 timed out"
> warning.
>
> This patch remedies the problem by changing q_len to a u32.
>
> Signed-off-by: Dean Nelson <[email protected]>
Applied, thanks.
Another way to solve this could have been to encode that length
as "length - 1"
On 02/08/2018 02:34 PM, David Miller wrote:
> From: Dean Nelson <[email protected]>
> Date:
>
>> 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 beginning
>> 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 go
>> beyond the end of the ring, causing various ills. Usually the first thing that
>> shows up is a "NETDEV WATCHDOG: enP2p1s0f1 (nicvf): transmit queue 7 timed out"
>> warning.
>>
>> This patch remedies the problem by changing q_len to a u32.
>>
>> Signed-off-by: Dean Nelson <[email protected]>
>
> 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
route.
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
applied?
Thanks,
Dean
On Fri, Feb 9, 2018 at 3:27 AM, Dean Nelson <[email protected]> wrote:
> On 02/08/2018 02:34 PM, David Miller wrote:
>>
>> From: Dean Nelson <[email protected]>
>> Date:
>>
>>> 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
>>> beginning
>>> 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
>>> go
>>> beyond the end of the ring, causing various ills. Usually the first thing
>>> that
>>> shows up is a "NETDEV WATCHDOG: enP2p1s0f1 (nicvf): transmit queue 7
>>> timed out"
>>> warning.
>>>
>>> This patch remedies the problem by changing q_len to a u32.
>>>
>>> Signed-off-by: Dean Nelson <[email protected]>
>>
>>
>> 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
> route.
>
> 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
> applied?
Thanks for fixing this and i think the current patch is fine.
Thanks,
Sunil.
>
> Thanks,
> Dean
>
>
>
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 02/08/2018 10:29 PM, Sunil Kovvuri wrote:
> On Fri, Feb 9, 2018 at 3:27 AM, Dean Nelson <[email protected]> wrote:
>> On 02/08/2018 02:34 PM, David Miller wrote:
>>>
>>> From: Dean Nelson <[email protected]>
>>> Date:
>>>
>>>> The Cavium thunder nicvf driver supports rx/tx rings of up to 65536
>>>> entries per.
...
>>>
>>> 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
>> route.
>>
>> 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
>> applied?
>
> Thanks for fixing this and i think the current patch is fine.
You're welcome. And thanks for responding. So I'll leave things as they
are.