netdev - Re: Resource management for ndo_xdp_xmit (Was: [PATCH net] virtio_net: Account for tx bytes and packets on sending xdp

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Message-ID: <20190208180516.287f6ddc@cakuba.netronome.com>
Date:   Fri, 8 Feb 2019 18:05:16 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Saeed Mahameed <saeedm@...lanox.com>
Cc:     "brouer@...hat.com" <brouer@...hat.com>,
        "thoiland@...hat.com" <thoiland@...hat.com>,
        "hawk@...nel.org" <hawk@...nel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "borkmann@...earbox.net" <borkmann@...earbox.net>,
        Tariq Toukan <tariqt@...lanox.com>,
        "toke@...e.dk" <toke@...e.dk>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "mst@...hat.com" <mst@...hat.com>,
        "dsahern@...il.com" <dsahern@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "makita.toshiaki@....ntt.co.jp" <makita.toshiaki@....ntt.co.jp>
Subject: Re: Resource management for ndo_xdp_xmit (Was: [PATCH net]
 virtio_net: Account for tx bytes and packets on sending xdp_frames)

On Sat, 9 Feb 2019 00:18:31 +0000, Saeed Mahameed wrote:
> On Fri, 2019-02-08 at 15:17 -0800, Saeed Mahameed wrote:
> > On Thu, 2019-02-07 at 19:08 +0000, Saeed Mahameed wrote:  
> > > 
> > > So 
> > > 1) on dev_map_update_elem() we will call
> > > dev->dev->ndo_bpf() to notify the device on the intention to
> > > start/stop
> > > redirect, and wait for it to create/destroy the HW resources
> > > before/after actually updating the map
> > >   
> > 
> > silly me, dev_map_update_elem must be atomic, we can't hook driver
> > resource allocation to it, it must come as a separate request
> > (syscall)
> > from user space to request to create XDP redirect resources.
> >   
> 
> Well, it is possible to render dev_map_update_elem non-atomic and fail
> BPF programs who try to update it in the verifier
> check_map_func_compatibility.
> 
> if you know of any case where devmap needs to be updated from the BPF
> program please let me know.

Did we find a solution to non-map redirect?

Sorry if I missed the discussion, I couldn't make the iovisor call this
week due to travel.