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From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
Date: Fri, 12 Jan 2024 17:21:40 +0200 (EET)
To: Liming Sun <limings@nvidia.com>
cc: Vadim Pasternak <vadimp@nvidia.com>, 
    David Thompson <davthompson@nvidia.com>, 
    Hans de Goede <hdegoede@redhat.com>, Mark Gross <markgross@kernel.org>, 
    Dan Carpenter <dan.carpenter@linaro.org>, 
    platform-driver-x86@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3] Drop Tx network packet when Tx TmFIFO is full
In-Reply-To: <20240111173106.96958-1-limings@nvidia.com>
Message-ID: <107b5fda-d3ec-48c1-107e-53502a1de0bd@linux.intel.com>
References: <f250079635da4ba75c3a3a1d7c3820f48cfc3f06.1704380474.git.limings@nvidia.com> <20240111173106.96958-1-limings@nvidia.com>
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On Thu, 11 Jan 2024, Liming Sun wrote:

> Starting from Linux 5.16 kernel, Tx timeout mechanism was added
> in the virtio_net driver which prints the "Tx timeout" warning
> message when a packet stays in Tx queue for too long. Below is an
> example of the reported message:
>=20
> "[494105.316739] virtio_net virtio1 tmfifo_net0: TX timeout on
> queue: 0, sq: output.0, vq: 0=C3=971, name: output.0, usecs since
> last trans: 3079892256".
>=20
> This issue could happen when external host driver which drains the
> FIFO is restared, stopped or upgraded. To avoid such confusing
> "Tx timeout" messages, this commit adds logic to drop the outstanding
> Tx packet if it's not able to transmit in two seconds due to Tx FIFO
> full, which can be considered as congestion or out-of-resource drop.
>=20
> This commit also handles the special case that the packet is half-
> transmitted into the Tx FIFO. In such case, the packet is discarded
> with remaining length stored in vring->rem_padding. So paddings with
> zeros can be sent out when Tx space is available to maintain the
> integrity of the packet format. The padded packet will be dropped on
> the receiving side.
>=20
> Signed-off-by: Liming Sun <limings@nvidia.com>
> ---
> v2->v3:
>   Updates for Ilpo's comments:
>   - Revises commit message to avoid confusion.
> v2: Fixed formatting warning
> v1: Initial version

Thanks, the commit message makes much more sense now!

Reviewed-by: Ilpo J=C3=A4rvinen <ilpo.jarvinen@linux.intel.com>

--=20
 i.

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