Re: net: thunder: change q_len's type to handle max ring size

[Dean Nelson]

On 02/08/2018 10:29 PM, Sunil Kovvuri wrote:

On Fri, Feb 9, 2018 at 3:27 AM, Dean Nelson  wrote:

On 02/08/2018 02:34 PM, David Miller wrote:


From: Dean Nelson 
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.

Re: net: thunder: change q_len's type to handle max ring size

[Dean Nelson]

On 02/08/2018 10:29 PM, Sunil Kovvuri wrote:

On Fri, Feb 9, 2018 at 3:27 AM, Dean Nelson  wrote:

On 02/08/2018 02:34 PM, David Miller wrote:


From: Dean Nelson 
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.

Re: net: thunder: change q_len's type to handle max ring size

[Sunil Kovvuri]

On Fri, Feb 9, 2018 at 3:27 AM, Dean Nelson  wrote:
> On 02/08/2018 02:34 PM, David Miller wrote:
>>
>> From: Dean Nelson 
>> 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 
>>
>>
>> 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
> linux-arm-ker...@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: net: thunder: change q_len's type to handle max ring size

[Sunil Kovvuri]

On Fri, Feb 9, 2018 at 3:27 AM, Dean Nelson  wrote:
> On 02/08/2018 02:34 PM, David Miller wrote:
>>
>> From: Dean Nelson 
>> 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 
>>
>>
>> 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
> linux-arm-ker...@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: net: thunder: change q_len's type to handle max ring size

[Dean Nelson]

On 02/08/2018 02:34 PM, David Miller wrote:

From: Dean Nelson 
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 


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

Re: net: thunder: change q_len's type to handle max ring size

[Dean Nelson]

On 02/08/2018 02:34 PM, David Miller wrote:

From: Dean Nelson 
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 


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

Re: net: thunder: change q_len's type to handle max ring size

[David Miller]

From: Dean Nelson 
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 

Applied, thanks.

Another way to solve this could have been to encode that length
as "length - 1"

Re: net: thunder: change q_len's type to handle max ring size

[David Miller]

From: Dean Nelson 
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 

Applied, thanks.

Another way to solve this could have been to encode that length
as "length - 1"