On 2024-10-04 03:34, Taehee Yoo wrote:
> On Fri, Oct 4, 2024 at 3:43 AM Mina Almasry <almasrymina@xxxxxxxxxx> wrote:
>>> @@ -3608,9 +3629,11 @@ static void bnxt_free_rx_rings(struct bnxt *bp)
>>>
>>> static int bnxt_alloc_rx_page_pool(struct bnxt *bp,
>>> struct bnxt_rx_ring_info *rxr,
>>> + int queue_idx,
>>> int numa_node)
>>> {
>>> struct page_pool_params pp = { 0 };
>>> + struct netdev_rx_queue *rxq;
>>>
>>> pp.pool_size = bp->rx_agg_ring_size;
>>> if (BNXT_RX_PAGE_MODE(bp))
>>> @@ -3621,8 +3644,15 @@ static int bnxt_alloc_rx_page_pool(struct bnxt *bp,
>>> pp.dev = &bp->pdev->dev;
>>> pp.dma_dir = bp->rx_dir;
>>> pp.max_len = PAGE_SIZE;
>>> - pp.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV;
>>> + pp.order = 0;
>>> +
>>> + rxq = __netif_get_rx_queue(bp->dev, queue_idx);
>>> + if (rxq->mp_params.mp_priv)
>>> + pp.flags = PP_FLAG_DMA_MAP | PP_FLAG_ALLOW_UNREADABLE_NETMEM;
>>
>> This is not the intended use of PP_FLAG_ALLOW_UNREADABLE_NETMEM.
>>
>> The driver should set PP_FLAG_ALLOW_UNREADABLE_NETMEM when it's able
>> to handle unreadable netmem, it should not worry about whether
>> rxq->mp_params.mp_priv is set or not.
>>
>> You should set PP_FLAG_ALLOW_UNREADABLE_NETMEM when HDS is enabled.
>> Let core figure out if mp_params.mp_priv is enabled. All the driver
>> needs to report is whether it's configured to be able to handle
>> unreadable netmem (which practically means HDS is enabled).
>
> The reason why the branch exists here is the PP_FLAG_ALLOW_UNREADABLE_NETMEM
> flag can't be used with PP_FLAG_DMA_SYNC_DEV.
>
> 228 if (pool->slow.flags & PP_FLAG_DMA_SYNC_DEV) {
> 229 /* In order to request DMA-sync-for-device the page
> 230 * needs to be mapped
> 231 */
> 232 if (!(pool->slow.flags & PP_FLAG_DMA_MAP))
> 233 return -EINVAL;
> 234
> 235 if (!pool->p.max_len)
> 236 return -EINVAL;
> 237
> 238 pool->dma_sync = true; //here
> 239
> 240 /* pool->p.offset has to be set according to the address
> 241 * offset used by the DMA engine to start copying rx data
> 242 */
> 243 }
>
> If PP_FLAG_DMA_SYNC_DEV is set, page->dma_sync is set to true.
>
> 347 int mp_dmabuf_devmem_init(struct page_pool *pool)
> 348 {
> 349 struct net_devmem_dmabuf_binding *binding = pool->mp_priv;
> 350
> 351 if (!binding)
> 352 return -EINVAL;
> 353
> 354 if (!pool->dma_map)
> 355 return -EOPNOTSUPP;
> 356
> 357 if (pool->dma_sync) //here
> 358 return -EOPNOTSUPP;
> 359
> 360 if (pool->p.order != 0)
> 361 return -E2BIG;
> 362
> 363 net_devmem_dmabuf_binding_get(binding);
> 364 return 0;
> 365 }
>
> In the mp_dmabuf_devmem_init(), it fails when pool->dma_sync is true.
This won't work for io_uring zero copy into user memory. We need all
PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | PP_FLAG_ALLOW_UNREADABLE_NETMEM
set.
I agree with Mina that the driver should not be poking at the mp_priv
fields. How about setting all the flags and then letting the mp->init()
figure it out? mp_dmabuf_devmem_init() is called within page_pool_init()
so as long as it resets dma_sync if set I don't see any issues.
>
> tcp-data-split can be used for normal cases, not only devmem TCP case.
> If we enable tcp-data-split and disable devmem TCP, page_pool doesn't
> have PP_FLAG_DMA_SYNC_DEV.
> So I think mp_params.mp_priv is still useful.
>
> Thanks a lot,
> Taehee Yoo
>
>>
>>
>> --
>> Thanks,
>> Mina
