From: Simon Horman <horms@kernel.org>
To: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
Cc: kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
decui@microsoft.com, longli@microsoft.com, andrew+netdev@lunn.ch,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, dipayanroy@linux.microsoft.com,
ssengar@linux.microsoft.com, jacob.e.keller@intel.com,
gargaditya@linux.microsoft.com, kees@kernel.org,
linux-hyperv@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH net] net: mana: Fall back to standard MTU when PF reports adapter_mtu of 0
Date: Mon, 22 Jun 2026 11:41:03 +0100 [thread overview]
Message-ID: <20260622104103.GA827683@horms.kernel.org> (raw)
In-Reply-To: <20260619055348.467224-1-ernis@linux.microsoft.com>
On Thu, Jun 18, 2026 at 10:53:38PM -0700, Erni Sri Satya Vennela wrote:
> Commit d7709812e13d ("net: mana: hardening: Validate adapter_mtu from
> MANA_QUERY_DEV_CONFIG") rejected any adapter_mtu value smaller than
> ETH_MIN_MTU + ETH_HLEN, including 0, returning -EPROTO and failing
> mana_probe().
>
> Some older PF firmware versions still in the field report
> adapter_mtu as 0 in the MANA_QUERY_DEV_CONFIG response. With the
> hardening check in place, the MANA VF driver now fails to load on
> those hosts, breaking networking entirely for guests.
>
> MANA hardware always supports the standard Ethernet MTU. Treat a
> reported adapter_mtu of 0 as "the PF did not advertise a value" and
> fall back to ETH_FRAME_LEN, the same value used for the pre-V2
> message version path. Only jumbo frames remain unavailable until
> the PF reports a valid MTU.
>
> Other small-but-nonzero bogus values are still rejected, preserving
> the original protection against the unsigned-subtraction wrap that
> would otherwise let ndev->max_mtu underflow to a huge value.
>
> Fixes: d7709812e13d ("net: mana: hardening: Validate adapter_mtu from MANA_QUERY_DEV_CONFIG")
> Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
Reviewed-by: Simon Horman <horms@kernel.org>
FTR, I agree with your assessment that the issue flagged in the
AI-generated review of this patch on sashiko.dev can be
treated as a follow-up [1].
And I don't think the low priority issue flagged in the AI-generated
review on https://netdev-ai.bots.linux.dev/sashiko/ should impede progress
of this patch.
[1] https://lore.kernel.org/bpf/ajj+5mhswcqhI2z7@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net/
prev parent reply other threads:[~2026-06-22 10:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-19 5:53 [PATCH net] net: mana: Fall back to standard MTU when PF reports adapter_mtu of 0 Erni Sri Satya Vennela
2026-06-20 5:54 ` sashiko-bot
2026-06-22 9:22 ` Erni Sri Satya Vennela
2026-06-22 10:41 ` Simon Horman [this message]
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