> -----Original Message----- > From: Stephen Hemminger [mailto:[email protected]] > Sent: Friday, December 20, 2024 12:16 AM > To: Wangyunjian(wangyunjian,TongTu) <[email protected]> > Cc: [email protected]; [email protected]; [email protected]; > Lilijun (Jerry) <[email protected]>; xiawei (H) <[email protected]>; > wangzengyuan <[email protected]>; [email protected] > Subject: Re: [PATCH 1/1] vhost: fix a double fetch when dequeue offloading > > On Thu, 19 Dec 2024 14:38:28 +0800 > Yunjian Wang <[email protected]> wrote: > > > - hdr = (struct virtio_net_hdr > > *)((uintptr_t)buf_vec[0].buf_addr); > > + rte_memcpy((void *)(uintptr_t)&tmp_hdr, > > + (void *)(uintptr_t)buf_vec[0].buf_addr, > > + sizeof(struct virtio_net_hdr)); > > } > > Do not introduce more rte_memcpy of a fixed size. > You don't need that many casts! > Why can you not use a structure assignment here.
The virtio_hdr is a shared component, and other fields within it are read multiple times. This can potentially result in a double fetch scenario.
