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Date: Mon, 22 Jun 2020 15:50:39 +0300
From: Denis Kirjanov <kda@...ux-powerpc.org>
To: paul@....org
Cc: netdev@...r.kernel.org, brouer@...hat.com, jgross@...e.com,
wei.liu@...nel.org, ilias.apalodimas@...aro.org
Subject: Re: [PATCH net-next v10 3/3] xen networking: add XDP offset
adjustment to xen-netback
On 6/22/20, Paul Durrant <xadimgnik@...il.com> wrote:
>> -----Original Message-----
>> From: Denis Kirjanov <kda@...ux-powerpc.org>
>> Sent: 22 June 2020 10:21
>> To: netdev@...r.kernel.org
>> Cc: brouer@...hat.com; jgross@...e.com; wei.liu@...nel.org; paul@....org;
>> ilias.apalodimas@...aro.org
>> Subject: [PATCH net-next v10 3/3] xen networking: add XDP offset
>> adjustment to xen-netback
>>
>> the patch basically adds the offset adjustment and netfront
>> state reading to make XDP work on netfront side.
>>
>> Signed-off-by: Denis Kirjanov <kda@...ux-powerpc.org>
>> ---
>> drivers/net/xen-netback/common.h | 4 ++++
>> drivers/net/xen-netback/interface.c | 2 ++
>> drivers/net/xen-netback/netback.c | 7 +++++++
>> drivers/net/xen-netback/rx.c | 15 ++++++++++++++-
>> drivers/net/xen-netback/xenbus.c | 32
>> ++++++++++++++++++++++++++++++++
>> 5 files changed, 59 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/xen-netback/common.h
>> b/drivers/net/xen-netback/common.h
>> index 05847eb..f14dc10 100644
>> --- a/drivers/net/xen-netback/common.h
>> +++ b/drivers/net/xen-netback/common.h
>> @@ -281,6 +281,9 @@ struct xenvif {
>> u8 ipv6_csum:1;
>> u8 multicast_control:1;
>>
>> + /* headroom requested by xen-netfront */
>> + u16 netfront_xdp_headroom;
>> +
>> /* Is this interface disabled? True when backend discovers
>> * frontend is rogue.
>> */
>> @@ -395,6 +398,7 @@ static inline pending_ring_idx_t
>> nr_pending_reqs(struct xenvif_queue *queue)
>> irqreturn_t xenvif_interrupt(int irq, void *dev_id);
>>
>> extern bool separate_tx_rx_irq;
>> +extern bool provides_xdp_headroom;
>>
>> extern unsigned int rx_drain_timeout_msecs;
>> extern unsigned int rx_stall_timeout_msecs;
>> diff --git a/drivers/net/xen-netback/interface.c
>> b/drivers/net/xen-netback/interface.c
>> index 0c8a02a..fc16edd 100644
>> --- a/drivers/net/xen-netback/interface.c
>> +++ b/drivers/net/xen-netback/interface.c
>> @@ -483,6 +483,8 @@ struct xenvif *xenvif_alloc(struct device *parent,
>> domid_t domid,
>> vif->queues = NULL;
>> vif->num_queues = 0;
>>
>> + vif->netfront_xdp_headroom = 0;
>> +
>
Hi Paul,
> How about just 'xdp_headroom'? It's shorter to type :-)
makes sense.
>
>> spin_lock_init(&vif->lock);
>> INIT_LIST_HEAD(&vif->fe_mcast_addr);
>>
>> diff --git a/drivers/net/xen-netback/netback.c
>> b/drivers/net/xen-netback/netback.c
>> index 315dfc6..6dfca72 100644
>> --- a/drivers/net/xen-netback/netback.c
>> +++ b/drivers/net/xen-netback/netback.c
>> @@ -96,6 +96,13 @@
>> module_param_named(hash_cache_size, xenvif_hash_cache_size, uint, 0644);
>> MODULE_PARM_DESC(hash_cache_size, "Number of flows in the hash cache");
>>
>> +/* The module parameter tells that we have to put data
>> + * for xen-netfront with the XDP_PACKET_HEADROOM offset
>> + * needed for XDP processing
>> + */
>> +bool provides_xdp_headroom = true;
>> +module_param(provides_xdp_headroom, bool, 0644);
>> +
>> static void xenvif_idx_release(struct xenvif_queue *queue, u16
>> pending_idx,
>> u8 status);
>>
>> diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c
>> index ef58870..c5e9e14 100644
>> --- a/drivers/net/xen-netback/rx.c
>> +++ b/drivers/net/xen-netback/rx.c
>> @@ -258,6 +258,19 @@ static void xenvif_rx_next_skb(struct xenvif_queue
>> *queue,
>> pkt->extra_count++;
>> }
>>
>> + if (queue->vif->netfront_xdp_headroom) {
>> + struct xen_netif_extra_info *extra;
>> +
>> + extra = &pkt->extras[XEN_NETIF_EXTRA_TYPE_XDP - 1];
>> +
>> + memset(extra, 0, sizeof(struct xen_netif_extra_info));
>> + extra->u.xdp.headroom = queue->vif->netfront_xdp_headroom;
>> + extra->type = XEN_NETIF_EXTRA_TYPE_XDP;
>> + extra->flags = 0;
>> +
>> + pkt->extra_count++;
>> + }
>> +
>> if (skb->sw_hash) {
>> struct xen_netif_extra_info *extra;
>>
>> @@ -356,7 +369,7 @@ static void xenvif_rx_data_slot(struct xenvif_queue
>> *queue,
>> struct xen_netif_rx_request *req,
>> struct xen_netif_rx_response *rsp)
>> {
>> - unsigned int offset = 0;
>> + unsigned int offset = queue->vif->netfront_xdp_headroom;
>> unsigned int flags;
>>
>> do {
>> diff --git a/drivers/net/xen-netback/xenbus.c
>> b/drivers/net/xen-netback/xenbus.c
>> index 286054b..c67abc5 100644
>> --- a/drivers/net/xen-netback/xenbus.c
>> +++ b/drivers/net/xen-netback/xenbus.c
>> @@ -393,6 +393,22 @@ static void set_backend_state(struct backend_info
>> *be,
>> }
>> }
>>
>> +static void read_xenbus_frontend_xdp(struct backend_info *be,
>> + struct xenbus_device *dev)
>> +{
>> + struct xenvif *vif = be->vif;
>> + u16 headroom;
>> + int err;
>> +
>> + err = xenbus_scanf(XBT_NIL, dev->otherend,
>> + "netfront-xdp-headroom", "%hu", &headroom);
>
> Isn't it just "xdp-headroom"? That's what the comments in netif.h state.
>
>> + if (err < 0) {
>> + vif->netfront_xdp_headroom = 0;
>> + return;
>> + }
>
> What is a reasonable value for maximum headroom? Do we really want to allow
> values all the way up to 65535?
Since the headroom is used for encapsulation I think we definitely
don't need more than 65535
but more that 255
>
> Paul
>
>> + vif->netfront_xdp_headroom = headroom;
>> +}
>> +
>> /**
>> * Callback received when the frontend's state changes.
>> */
>> @@ -417,6 +433,11 @@ static void frontend_changed(struct xenbus_device
>> *dev,
>> set_backend_state(be, XenbusStateConnected);
>> break;
>>
>> + case XenbusStateReconfiguring:
>> + read_xenbus_frontend_xdp(be, dev);
>> + xenbus_switch_state(dev, XenbusStateReconfigured);
>> + break;
>> +
>> case XenbusStateClosing:
>> set_backend_state(be, XenbusStateClosing);
>> break;
>> @@ -947,6 +968,8 @@ static int read_xenbus_vif_flags(struct backend_info
>> *be)
>> vif->ipv6_csum = !!xenbus_read_unsigned(dev->otherend,
>> "feature-ipv6-csum-offload", 0);
>>
>> + read_xenbus_frontend_xdp(be, dev);
>> +
>> return 0;
>> }
>>
>> @@ -1036,6 +1059,15 @@ static int netback_probe(struct xenbus_device
>> *dev,
>> goto abort_transaction;
>> }
>>
>> + /* we can adjust a headroom for netfront XDP processing */
>> + err = xenbus_printf(xbt, dev->nodename,
>> + "feature-xdp-headroom", "%d",
>> + provides_xdp_headroom);
>> + if (err) {
>> + message = "writing feature-xdp-headroom";
>> + goto abort_transaction;
>> + }
>> +
>> /* We don't support rx-flip path (except old guests who
>> * don't grok this feature flag).
>> */
>> --
>> 1.8.3.1
>
>
>
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