Re: [dpdk-dev] [PATCH BUG 335 3/3] net/virtio: fix compilation error with 0 headroom

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 7/26/19 2:25 PM, Olivier Matz wrote:
> Hi,
> 
> On Thu, Jul 25, 2019 at 04:36:45PM +0530, Hemant Agrawal wrote:
>> When using RTE_PKTMBUF_HEADROOM as 0, virito ethdev driver throws
>> compilation error
>> virtio_ethdev.c:1851:2: note: in expansion of macro ‘RTE_BUILD_BUG_ON’
>> RTE_BUILD_BUG_ON(RTE_PKTMBUF_HEADROOM
>> 	< sizeof(struct virtio_net_hdr_mrg_rxbuf));
>>
>> This patch change it into run-time check.
>> Reported as: https://bugs.dpdk.org/show_bug.cgi?id=335
>>
>> Fixes: 198ab33677c9 ("net/virtio: move device initialization in a function")
> 
> I think the proper commit is:
> Fixes: dec08c28c0b3 ("virtio: check packet headroom at compile time")

Indeed.

> It looks this patch more or less reverts this old commit.
> +CC Stephen

I wonder whether we could have a warning at build time so that the one
who builds DPDK is aware some driver may not be usable, in addition to
the below patch that fails virtio-net init.

Any thoughts?

Thanks,
Maxime

>> Cc: stable@dpdk.org
>> Cc: Olivier Matz <olivier.matz@6wind.com>
>>
>> Signed-off-by: Hemant Agrawal <hemant.agrawal@nxp.com>
>> ---
>>   drivers/net/virtio/virtio_ethdev.c | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c
>> index 62c827443..3e2e8bd2a 100644
>> --- a/drivers/net/virtio/virtio_ethdev.c
>> +++ b/drivers/net/virtio/virtio_ethdev.c
>> @@ -1848,7 +1848,14 @@ eth_virtio_dev_init(struct rte_eth_dev *eth_dev)
>>   	struct virtio_hw *hw = eth_dev->data->dev_private;
>>   	int ret;
>>   
>> -	RTE_BUILD_BUG_ON(RTE_PKTMBUF_HEADROOM < sizeof(struct virtio_net_hdr_mrg_rxbuf));
>> +	if (sizeof(struct virtio_net_hdr_mrg_rxbuf) > RTE_PKTMBUF_HEADROOM) {
>> +		PMD_INIT_LOG(ERR,
>> +			"Not sufficient headroom required = %d, avail = %d",
>> +			(int)sizeof(struct virtio_net_hdr_mrg_rxbuf),
>> +			RTE_PKTMBUF_HEADROOM);
>> +
>> +		return -1;
>> +	}
>>   
>>   	eth_dev->dev_ops = &virtio_eth_dev_ops;
>>   
>> -- 
>> 2.17.1
>>
>