From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EAC704EE87F for ; Wed, 16 Sep 2026 12:35:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789562108; cv=none; b=mrZWmhVV4Y84Y+kHvAmBnIzkII9UA4cRYvILwchQqAMDWqQbOb+D7cdO6Xz7nRKEQDY8W17WdztE7d8rEe42ONjIAFh/zHILqkEDKDxFJXOKIEmRsNsLz8B7S0uFqz1gbRmzDZ5Xs9mmYMgcjZXUXW2BSW/ovkztKX5lX4G0l0Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789562108; c=relaxed/simple; bh=VCLKLWhXdt113SN5py48YYJpfZW5pOKUyWyENVGV2Bk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=uCgueT8Z/YDd/0f4WI4DqIESRDlvgFik4gm9iJHTAf8Xms0g3rJ+jfsYNHiZmNRShor5o1xSpKgtmh2UwtVBcPeqo2MHXBZAoGPDBjlKD5DMOISAir3Qm+YeQkqSeONhk9cEVeP6xq+arGCUDmyfcnF07q0qhUd2Dc2IIrqa2h8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JOPUhVNM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JOPUhVNM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98EA51F000FF; Wed, 16 Sep 2026 12:35:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789562105; bh=YNB/s1mswh64q12U6Hacif3SbRQSsxBfLpW75bfhJA4=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=JOPUhVNM8fxTnS8AZrznLsLnbvEYOk4AR8I1lvYWRgAKLdVMuRb4EAlVA5GE4vv// Osj8v09uMCPAFs0to4mRuCtpWab7ueaREwEMM13HiNUtu6252NtErhXk2yr49OgV1T y88FFP+bw9OzJBaVkQZ7MTIsIIqDjNadvAWDaQiI312J3128ravAzDUwhQqtAuA7h6 94F9jVdULkmHvm7ML9GZVnGgOmcYfREAFLbk23Xp7naIfZpNI9xr2wJDKeLeBLz6MT lXZRAfR9nI4GV52uy2uacthfv/5EtngamcbF4jWsd3400LL7jqxFlgPVuIGgu3iDql OGMsOUui1WKwQ== Date: Wed, 16 Sep 2026 13:35:01 +0100 From: Simon Horman To: Jakub Kicinski Cc: davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, Alexander Duyck Subject: Re: [PATCH net] eth: fbnic: ring the doorbell if a burst ends in a drop Message-ID: <20260916123501.GE51261@horms.kernel.org> References: <20260915022327.913218-1-kuba@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260915022327.913218-1-kuba@kernel.org> On Mon, Sep 14, 2026 at 07:23:27PM -0700, Jakub Kicinski wrote: > fbnic_tx_map() skips the doorbell write, and the completion request, > for every packet handed to it with xmit_more set, counting on the > packet which ends the burst to publish them all. When that packet is > dropped instead - skb_put_padto(), skb_cow_head() or a DMA mapping > failure - nothing rings. The descriptors of the preceding packets stay > invisible to the HW until the next transmit on that queue, which for a > burst-then-idle workload may never come. > > Remember the meta descriptor of the last packet left without a doorbell > and flush it from the error paths. The completion request has to be set > on that descriptor rather than simply writing the tail, otherwise the HW > would transmit the packets but never report a head, and the ring would > fill up and stall for good. > > This is very similar to Joe's recent series of fixes for bnxt. > Not seen in real life, reproduced under QEMU with failure injection. > > Fixes: 9a57bacd574b ("eth: fbnic: Add basic Tx handling") > Reviewed-by: Alexander Duyck > Signed-off-by: Jakub Kicinski > --- > Reproduced under the QEMU fbnic model by failing the DMA mapping of the > last segment of a software-GSO burst: 21 descriptors (7 packets) stayed > in the ring with head stuck at 24 and tail at 45, 10094 bytes stuck in > BQL, and QEMU saw none of the 7 frames. Reviewed-by: Simon Horman