netdev - Re: [PATCH 1/3] virtio: dwords->qwords

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Message-ID: <c4aa4304-b675-4a60-bb7e-adcf26a8694d@lunn.ch>
Date: Sat, 11 Oct 2025 20:52:18 +0200
From: Andrew Lunn <andrew@...n.ch>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>, Jason Wang <jasowang@...hat.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Jonathan Corbet <corbet@....net>, kvm@...r.kernel.org,
	virtualization@...ts.linux.dev, linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/3] virtio: dwords->qwords

> That's not spec, that's linux driver. The spec is the source of truth.

Right, lets follow this.

I'm looking at

https://docs.oasis-open.org/virtio/virtio/v1.3/csd01/virtio-v1.3-csd01.html

Is that correct?

That document does not have a definition of word. However, what is
interesting is section "4.2.2 MMIO Device Register Layout"

DeviceFeaturesSel 0x014

Device (host) features word selection.
Writing to this register selects a set of 32 device feature bits accessible by reading from DeviceFeatures.

and

DriverFeaturesSel 0x024

Activated (guest) features word selection
Writing to this register selects a set of 32 activated feature bits accessible by writing to DriverFeatures.

I would interpret this as meaning a feature word is a u32. Hence a
DWORD is a u64, as the current code uses.

	Andrew