Thx Christoph On Wed, Aug 21, 2019 at 10:17 AM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > On Tue, Aug 20, 2019 at 08:34:29PM +0800, guoren@xxxxxxxxxx wrote: > > From: Guo Ren <ren_guo@xxxxxxxxx> > > > > We prohibit non-aligned access in kernel mode, but some special NIC > > driver needs to support kernel-state unaligned access. For example, > > when the bus does not support unaligned access, IP header parsing > > will cause non-aligned access and driver does not recopy the skb > > buffer to dma for performance reasons. > > > > Added kernel_enable & user_enable to control unaligned access and > > added kernel_count & user_count for statistical unaligned access. > > If the NIC drivers requires this it is buggy. Yes, you are right, but I've no control on their non-upstreamed drivers. Every time kernel version updated I need to take care of that issue for them. So just give them a back door in arch/csky and they could disable it by manual. > Kernel code must > use the get_unaligned* / put_unaligned* helpers for that. Most of ethernet drivers use netdev_alloc_skb_ip_align() to let hardware deal with unaligned access, but some NICs couldn't and we may modify kernel's skb_ip_header parsing code with get_unaligned*/put_unaligned* ? -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/
