> -----Original Message----- > From: Jakub Kicinski <kuba@xxxxxxxxxx> > Sent: Thursday, January 23, 2020 12:30 PM > To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > Cc: sashal@xxxxxxxxxx; linux-hyperv@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; > KY Srinivasan <kys@xxxxxxxxxxxxx>; Stephen Hemminger > <sthemmin@xxxxxxxxxxxxx>; olaf@xxxxxxxxx; vkuznets > <vkuznets@xxxxxxxxxx>; davem@xxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH V3,net-next, 1/2] hv_netvsc: Add XDP support > > On Thu, 23 Jan 2020 17:14:06 +0000, Haiyang Zhang wrote: > > > > Changes: > > > > v3: Minor code and comment updates. > > > > v2: Added XDP_TX support. Addressed review comments. > > > > > > How does the locking of the TX path work? You seem to be just > > > calling the normal xmit method, but you don't hold the xmit queue > > > lock, so the stack can start xmit concurrently, no? > > > > The netvsc and vmbus can handle concurrent transmits, except the msd > > (Multi-Send Data) field which can only be used by one queue. > > > > I already added a new flag to netvsc_send(), so packets from XDP_TX > > won't use the msd. > > I see, there's a few non-atomic counters there, but maybe that's not a big deal. Yes, those error counters are used less frequently, and not necessary to be precise. > What frees the skb if the ring is full, and netvsc_send_pkt() returns -EAGAIN? > Nothing checks the return value from netvsc_xdp_xmit(). Good catch! I will add skb free when -EAGAIN is returned for XDP_TX. I will update the patch. Thanks, - Haiyang
