From: Jakub Kicinski <kuba@xxxxxxxxxx> Sent: Wednesday, February 1, 2023 9:01 PM
>
> On Mon, 30 Jan 2023 19:33:06 -0800 Michael Kelley wrote:
> > @@ -990,9 +987,7 @@ static int netvsc_dma_map(struct hv_device *hv_dev,
> > struct hv_netvsc_packet *packet,
> > struct hv_page_buffer *pb)
> > {
> > - u32 page_count = packet->cp_partial ?
> > - packet->page_buf_cnt - packet->rmsg_pgcnt :
> > - packet->page_buf_cnt;
> > + u32 page_count = packet->page_buf_cnt;
> > dma_addr_t dma;
> > int i;
>
> Suspiciously, the caller still does:
>
> if (packet->cp_partial)
> pb += packet->rmsg_pgcnt;
>
> ret = netvsc_dma_map(ndev_ctx->device_ctx, packet, pb);
>
> Shouldn't that if () pb +=... also go away?
No -- it's correct.
In netvsc_send(), cp_partial is tested and packet->page_buf_cnt is
adjusted. But the pointer into the pagebuf array is not adjusted in
netvsc_send(). Instead it is adjusted here in netvsc_send_pkt(), which
brings it back in sync with packet->page_buf_cnt.
I don't know if there's a good reason for the adjustment being split
across two different functions. It doesn't seem like the most
straightforward approach. From a quick glance at the code it looks
like this adjustment to 'pb' could move to netvsc_send() to be
together with the adjustment to packet->page_buf_cnt, but maybe
there's a reason for the split that I'm not familiar with.
Haiyang -- any insight?
Michael
