On Thu, 29 Feb 2024 at 13:52, wangyunjian <[email protected]> wrote: > > > -----Original Message----- > > From: Paolo Abeni [mailto:[email protected]] > > Sent: Thursday, February 29, 2024 6:43 PM > > To: wangyunjian <[email protected]>; [email protected]; > > [email protected]; [email protected]; [email protected]; > > [email protected]; [email protected]; [email protected]; > > [email protected]; [email protected] > > Cc: [email protected]; [email protected]; > > [email protected]; [email protected]; > > [email protected]; xudingke <[email protected]>; liwei (DT) > > <[email protected]> > > Subject: Re: [PATCH net-next v2 1/3] xsk: Remove non-zero 'dma_page' check > > in > > xp_assign_dev > > > > On Wed, 2024-02-28 at 19:05 +0800, Yunjian Wang wrote: > > > Now dma mappings are used by the physical NICs. However the vNIC maybe > > > do not need them. So remove non-zero 'dma_page' check in > > > xp_assign_dev. > > > > > > Signed-off-by: Yunjian Wang <[email protected]> > > > --- > > > net/xdp/xsk_buff_pool.c | 7 ------- > > > 1 file changed, 7 deletions(-) > > > > > > diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c index > > > ce60ecd48a4d..a5af75b1f43c 100644 > > > --- a/net/xdp/xsk_buff_pool.c > > > +++ b/net/xdp/xsk_buff_pool.c > > > @@ -219,16 +219,9 @@ int xp_assign_dev(struct xsk_buff_pool *pool, > > > if (err) > > > goto err_unreg_pool; > > > > > > - if (!pool->dma_pages) { > > > - WARN(1, "Driver did not DMA map zero-copy buffers"); > > > - err = -EINVAL; > > > - goto err_unreg_xsk; > > > - } > > > > This would unconditionally remove an otherwise valid check for most NIC. > > What > > about let the driver declare it wont need DMA map with a > > (pool?) flag. > > This check is redundant. The NIC's driver determines whether a DMA map is > required. > If the NIC'driver requires the DMA map, it uses the xsk_pool_dma_map > function, which > initializes the DMA map and performs a check.
Just to provide some context: I put this check there many years ago to guard against a zero-copy driver writer forgetting to call xsk_pool_dma_map() during the implementation phase. A working driver will always have pool->dma_pages != NULL. If you both think that this check is too much of a precaution, then I have no problem getting rid of it. Just thought that a text warning would be nicer than a crash later. Thanks: Magnus > Thanks > > > > > Cheers, > > > > Paolo >
