Re: [dpdk-dev] [PATCH] net/ixgbe: clear registers of all queues on VF reset

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 1/5/2021 12:52 PM, Wang, Haiyue wrote:
>> -----Original Message-----
>> From: Ferruh Yigit <ferruh.yigit@intel.com>
>> Sent: Tuesday, January 5, 2021 18:30
>> To: Simon Ellmann <simon.ellmann@tum.de>; Wang, Haiyue <haiyue.wang@intel.com>; Guo, Jia
>> <jia.guo@intel.com>
>> Cc: dev@dpdk.org
>> Subject: Re: [dpdk-dev] [PATCH] net/ixgbe: clear registers of all queues on VF reset
>>
>> On 1/5/2021 9:02 AM, Simon Ellmann wrote:
>>> On 1/4/21 4:56 PM, Ferruh Yigit wrote:
>>>
>>>> On 12/18/2020 2:34 AM, Wang, Haiyue wrote:
>>>>>> -----Original Message-----
>>>>>> From: Simon Ellmann <simon.ellmann@tum.de>
>>>>>> Sent: Friday, December 18, 2020 01:15
>>>>>> To: Guo, Jia <jia.guo@intel.com>; Wang, Haiyue <haiyue.wang@intel.com>
>>>>>> Cc: dev@dpdk.org; Simon Ellmann <simon.ellmann@tum.de>
>>>>>> Subject: [PATCH] net/ixgbe: clear registers of all queues on VF reset
>>>>>>
>>>>>> ixgbe devices support up to 8 Rx and Tx queues per virtual function.
>>>>>> Currently, the registers of only seven queues are set to default when
>>>>>> resetting a VF.
>>>>>>
>>>>>
>>>>> Fixes: d17d0b7a2407 ("ixgbe/base: reset VF registers")
>>>>> Cc: stable@dpdk.org
>>>>>
>>>>>> Signed-off-by: Simon Ellmann <simon.ellmann@tum.de>
>>>>>> ---
>>>>>>    drivers/net/ixgbe/base/ixgbe_vf.c | 2 +-
>>>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>
>>>>>
>>>>> Good catch, thanks!
>>>>>
>>>>> Acked-by: Haiyue Wang <haiyue.wang@intel.com>
>>>>>
>>>>
>>>> This seems a very long lived defect, I am just suspicious if there was a
>>>> reason to limit queue number to 7.
>>>>
>>>>
>>>> Simon,
>>>>
>>>> How did you find the defect? And did you test/verify it with the update?
>>>> (assuming you are using all 8 queues for the VF)
>>>
>>> Hi Ferruh,
>>>
>>> I was implementing ixgbevf for ixy.rs (https://ixy.rs/) by reading the code in
>>> DPDK and Linux. While doing that I noticed that DPDK was only resetting 7 queues
>>> which looked like a off-by-one error to me. I would have expected a comment if
>>> this behaviour was intentional. I haven't checked the update.
>>>
>>
>> Most probably you are right, but when I tried to test this, the HW I have
>> doesn't let me set more than 4 queues for the VF, so I was a little suspicious
>> about hardcoded 8 value.
>>
>> What do you think using 'hw->mac.max_rx_queues' instead? Which seems used a few
>> other places to walk the queues?
>>
>> Also can you please point the equivalent code in the Linux driver? As far as I
>> can see it also uses 'adapter->num_rx_queues', but I wonder if is there any
>> hardcoded value there.
>>
> 
> I found the original detail log:
> 
> ----
> ixgbevf: Clear VF registers we are required to configure anyway after VFLR
> 
> This function resets just about any register that could "possibly leak"
> any information from one VM instance to another.  The registers set it
> is returning to initial values is the same as those we are required
> to reconfigure after a VFLR anyway.  So this shouldn't affect any
> driver that is doing what it is suppose to.
> 
> ----
> 
> Also, the datasheet says it is '0 ... 7'
> 
> Receive DMA Registers,
> 
> 0x01000 + 0x40*n, n=0...7 VFRDBAL ...
> 
> So it should be safe to uses '8' to reset the VF hardware BAR0 information.
> The 'hw->mac.max_rx_queues' is about the software resource allocation in PF.
> 

Thanks Haiuye for the clarification, so I will proceed with the patch.