Re: [REGRESSION] Commit 447cbe95ebb9 causes IOMMU DMA faults on macvlan/vlan with bnxt_en

[Stefan Fleischmann <sfle@kth.se>]

On Sun, 4 Oct 2026 16:35:32 +0200
Stefan Fleischmann <sfle@kth.se> wrote:

> On Sun, 4 Oct 2026 13:46:08 +0200
> Eric Dumazet <edumazet@kernel.org> wrote:
> 
> 
> > 
> > Notice that 0xfc499000 is on an exact 4KB page boundary. This points
> > to a DMA read overrun where the Broadcom DMA engine reads past the
> > end of a buffer mapped in page 0xfc498xxx into the adjacent unmapped
> > page 0xfc499000.
> > 
> > Have you tried a recent net kernel ?  
> 
> Hi Eric,
> 
> that might be a bit tricky. We use ZFS on this server and the version
> we have installed only supports up to kernel 7.2.

Scratch that, I noticed that this even happens with none of the LXC
containers running. So I tested with the main branch from
 https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
 (commit 6dc989ea46b9)

Same issue.

Best,
Stefan

> > Could you please test whether disabling TSO or hardware VLAN
> > offload prevents the crash? (maybe adding one option at a time)
> > 
> >    # ethtool -K eno1np0 tso off
> > 
> >    # ethtool -K eno1np0 tx-vlan-offload off  
> 
> I tested this now and none of these options made a difference. I've
> also tested disabling other offloads, no difference.
> 
> Best,
> Stefan
> 
> > Adding Joe to this thread, because some parts in
> > tso_dma_map_init() or tso_start() might have bugs.
> > 
> > # Disable USO on the physical interface
> > ethtool -K eno1np0 tx-udp-segmentation off
> > 
> > This reminds me on a prior attempt I made months ago to sanitize
> > tso_start()
> > 
> > Note that my email address has changed to edumazet@kernel.org
> > 
> > Thanks.
> >