Re: [PATCH net-next v7 07/13] net: mana: swap queue sets in mana_change_mtu

[Wei Hu <weh@linux.microsoft.com>]

Hi,

> Does this stats update in mana_xdp_xmit() lack mutual exclusion when
> racing with other CPUs?

I will leave this counter update unchanged in v8. This is the same
baseline lost-update issue reported on patch 4: CPUs can share a queue,
and the aggregate xdp_xmit update is outside the per-frame send lock.
That exclusion gap predates this series in both upstream bases.

The seqcount-corruption/infinite-loop consequence requires the 32-bit
u64_stats_sync implementation. Supported PCI MANA configurations are
X86_64 or ARM64, and CDX requires 64BIT; their implementation has no
sequence counter or fetch retry loop. The lost increments are real, but
the more severe claimed consequence does not follow on those builds.

Also, the submitted patch 7 does not modify mana_bpf.c. The quoted
counter-pointer conversion belongs to an earlier patch in the series.
Neither that conversion nor this MTU change introduces the existing
writer-exclusion gap. I am keeping the independent counter fix out of v8.

Thanks,
Wei