Re: [Intel-wired-lan] [PATCH net-next v2 11/13] ice: introduce clear_reset_state operation

[Jacob Keller <jacob.e.keller@intel.com>]

On 1/19/2023 12:42 AM, Paul Menzel wrote:
> Dear Jacob,
> 
> 
> Thank you for your patch.
> 
> Am 19.01.23 um 02:16 schrieb Jacob Keller:
>> When hardware is reset, the VF relies on the VFGEN_RSTAT register to detect
>> when the VF is finished resetting. This is a tri-state register where 0
>> indicates a reset is in progress, 1 indicates the hardware is done
>> resetting, and 2 indicates that the software is done resetting.
>>
>> Currently the PF driver relies on the device hardware resetting VFGEN_RSTAT
>> when a global reset occurs. This works ok, but it does mean that the VF
>> might not immediately notice a reset when the driver first detects that the
>> global reset is occurring.
>>
>> This is also problematic for Scalable IOV, because there is no read/write
>> equivalent VFGEN_RSTAT register for the Scalable VSI type. Instead, the
>> Scalable IOV VFs will need to emulate this register.
>>
>> To support this, introduce a new VF operation, clear_reset_state, which is
>> called when the PF driver first detects a global reset. The Single Root IOV
>> implementation can just write to VFGEN_RSTAT to ensure its cleared
> 
> it’s
> 
>> immediately, without waiting for the actual hardware reset to begin. The
>> Scalable IOV implementation will use this as part of its tracking of the
>> reset status to allow properly reporting the emulated VFGEN_RSTAT to the VF
>> driver.
> 
> Can this be tested somehow? If yes, it’d be great if you added the recipe.
> 

The operation can be tested by triggering a device reset while having
VFs. But note that the ice driver does not yet support Scalable IOV. We
are working on this but are not yet ready to submit a series
implementing the support. Some of this series are patches intended to
aid in implementing Scalable IOV, and I am sending them now in order to
reduce the size and scope of the series that will actually finish the
implementation.

In general the reset behavior can be tested by adding a Single Root IOV
VF (via sriov_numvfs), and then triggering a reset. This can be done in
a variety of ways including by configuring some of the netlink VF
parameters like the trust setting, or by any operation on the PF that
triggers a PF reset. (Unfortunately I do not recall a specific example
offhand).

Thanks,
Jake
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