Re: [PATCH iwl-next v7 5/9] igc: Add support for frame preemption verification

["Abdul Rahim, Faizal" <faizal.abdul.rahim@linux.intel.com>]

On 4/3/2025 11:26 pm, Vladimir Oltean wrote:
> On Mon, Mar 03, 2025 at 05:26:54AM -0500, Faizal Rahim wrote:
>> +static inline bool igc_fpe_is_verify_or_response(union igc_adv_rx_desc *rx_desc,
>> +						 unsigned int size)
>> +{
>> +	u32 status_error = le32_to_cpu(rx_desc->wb.upper.status_error);
>> +	int smd;
>> +
>> +	smd = FIELD_GET(IGC_RXDADV_STAT_SMD_TYPE_MASK, status_error);
>> +
>> +	return (smd == IGC_RXD_STAT_SMD_TYPE_V || smd == IGC_RXD_STAT_SMD_TYPE_R) &&
>> +		size == SMD_FRAME_SIZE;
>> +}
> 
> The NIC should explicitly not respond to frames which have an SMD-V but
> are not "verify" mPackets (7 octets of 0x55 + 1 octet SMD-V + 60 octets
> of 0x00 + mCRC - as per 802.3 definitions). Similarly, it should only
> treat SMD-R frames which contain 7 octets of 0x55 + 1 octet SMD-R + 60
> octets of 0x00 + mCRC as "respond" mPackets, and only advance its
> verification state machine based on those.
> 
> Specifically, it doesn't look like you are ensuring the packet payload
> contains 60 octets of zeroes. Is this something that the hardware
> already does for you, or is it something that needs further validation
> and differentiation in software?

The hardware doesn’t handle this, so the igc driver have to do it manually. 
I missed this handling, and Chwee Lin also noticed the issue while testing 
this patch series—it wasn’t rejecting SMD-V and SMD-R with a non-zero 
payload. I’ll update this patch to include the fix that Chwee Lin 
implemented and tested. Thanks.