From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: [PATCH net-next] net/mlx4_en: Advertise HIGH DMA support only if dma mask is 64 bit Date: Mon, 12 Aug 2013 18:32:40 +0200 Message-ID: <1376325160.14079.59.camel@deadeye.wl.decadent.org.uk> References: <1376296230-12276-1-git-send-email-amirv@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: "David S. Miller" , , "Or Gerlitz" , Alexander Guller To: Amir Vadai Return-path: Received: from webmail.solarflare.com ([12.187.104.25]:33902 "EHLO webmail.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756189Ab3HLQcr (ORCPT ); Mon, 12 Aug 2013 12:32:47 -0400 In-Reply-To: <1376296230-12276-1-git-send-email-amirv@mellanox.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2013-08-12 at 11:30 +0300, Amir Vadai wrote: > Need to check that the pci device DMA mask was set to 64 bit support > (done by mlx4_core) before advertising HIGH DMA support in higher drivers. > Otherwise, may run into an issue that skb/frag/data is in high memory > and can't dma map it, thus packets are dropped. NETIF_F_HIGHDMA means that the driver can transmit skbs with page fragments in high memory, i.e. it doesn't require them to have an existing virtual mapping for the kernel. If I'm not mistaken, this should be cleared only for drivers that don't use DMA or kmap functions. On a 64-bit machine there is no highmem and without NETIF_F_HIGHDMA you can still be given pages at any physical address. On a 32-bit machine highmem usually starts at 1GB and I doubt you have any chips that are that limited in DMA range. :-) I really doubt this is the fix you're looking for. Ben. > Signed-off-by: Alexander Guller > Signed-off-by: Amir Vadai > --- > drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c > index fa37b7a..9568b77 100644 > --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c > +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c > @@ -2317,9 +2317,13 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port, > dev->vlan_features = dev->hw_features; > > dev->hw_features |= NETIF_F_RXCSUM | NETIF_F_RXHASH; > - dev->features = dev->hw_features | NETIF_F_HIGHDMA | > + dev->features = dev->hw_features | > NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_CTAG_RX | > NETIF_F_HW_VLAN_CTAG_FILTER; > + > + if (mdev->dev->pdev->dma_mask == DMA_BIT_MASK(64)) > + dev->features |= NETIF_F_HIGHDMA; > + > dev->hw_features |= NETIF_F_LOOPBACK; > > if (mdev->dev->caps.steering_mode == -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.