Re: [RFC PATCH 01/17] virtio_ring: Avoid reading unneeded used length

From: Johannes Berg
Date: Mon May 17 2021 - 05:15:24 EST

On Mon, 2021-05-17 at 17:08 +0800, Xie Yongji wrote:
> If device driver doesn't need used length, it can pass a NULL
> len in virtqueue_get_buf()/virtqueue_get_buf_ctx().

Well, actually, it can't right now?

You should probably rephrase this, saying something like

Allow passing NULL to len in ... if the device driver doesn't need
the length, and don't read it in that case.

or so?

> Then
> we can avoid reading and validating the len value in used
> ring entries.

Not sure what that "validating" is about, I only see reading?