Re: [Xen-devel] Xen-unstable Linux 3.14-rc3 and 3.13 Network troubles "bisected"

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Mar 12, 2014 at 03:23:36PM +0100, Sander Eikelenboom wrote:
[...]
> > From the look of the code, 0 looks correct to me. Netback won't complain
> > about "bad gref" because it has no idea what a "good gref" looks like.
> > Only Xen has the knowledge whether a gref is legit. All netback sees is
> > the hypercall fails and it tries to push corresponding response to
> > netfront. But you can probably safely assume a gref larger than several
> > thousands be bad.
> 
> OK it's indeed netback setting the status to -1:
> 
> [  976.431585] vif vif-7-0 vif7.0: ?!? xenvif_rx_action status err? status:-1 
> meta_slots_used:1 flags:3 size:958
> [ 1030.855057] vif vif-7-0 vif7.0: ?!? xenvif_rx_action status err? status:-1 
> meta_slots_used:2 flags:7 size:2974
> [ 1030.861759] vif vif-7-0 vif7.0: ?!? xenvif_add_frag_responses status err? 
> status:-1 i:0 nr_meta_slots:1 flags:0 size:1460
> [ 1030.868499] vif vif-7-0 vif7.0: ?!? xenvif_rx_action status err? status:-1 
> meta_slots_used:1 flags:3 size:958
> [ 1030.875278] vif vif-7-0 vif7.0: ?!? xenvif_rx_action status err? status:-1 
> meta_slots_used:1 flags:3 size:2974
> [ 1068.199650] vif vif-7-0 vif7.0: ?!? xenvif_rx_action status err? status:-1 
> meta_slots_used:8 flags:7 size:1634
> [ 1068.206479] vif vif-7-0 vif7.0: ?!? xenvif_add_frag_responses status err? 
> status:-1 i:0 nr_meta_slots:7 flags:4 size:2848
> [ 1068.213158] vif vif-7-0 vif7.0: ?!? xenvif_add_frag_responses status err? 
> status:-1 i:1 nr_meta_slots:7 flags:4 size:4096
> [ 1068.219701] vif vif-7-0 vif7.0: ?!? xenvif_add_frag_responses status err? 
> status:-1 i:2 nr_meta_slots:7 flags:4 size:4096
> [ 1068.226194] vif vif-7-0 vif7.0: ?!? xenvif_add_frag_responses status err? 
> status:-1 i:3 nr_meta_slots:7 flags:4 size:4096
> [ 1068.232728] vif vif-7-0 vif7.0: ?!? xenvif_add_frag_responses status err? 
> status:-1 i:4 nr_meta_slots:7 flags:4 size:4096
> [ 1068.239163] vif vif-7-0 vif7.0: ?!? xenvif_add_frag_responses status err? 
> status:-1 i:5 nr_meta_slots:7 flags:4 size:4096
> [ 1068.245397] vif vif-7-0 vif7.0: ?!? xenvif_add_frag_responses status err? 
> status:-1 i:6 nr_meta_slots:7 flags:0 size:1168
> [ 1068.251457] vif vif-7-0 vif7.0: ?!? xenvif_rx_action status err? status:-1 
> meta_slots_used:1 flags:3 size:958
> 
> Now to find out why ..
> 

-1 is the error code documented in netif.h, XEN_NETIF_RSP_ERROR.

grant copy fails -> netback sets response status to -1.

Assuming the traffic volumn is quite high both way (TX and RX), probably
worth checking if RX ring is overflowed. That is, if consumer pointer(s)
advance before producer pointer(s).

Wei.

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