On Wed, Jan 29, 2014 at 03:04:50PM +1030, Rusty Russell wrote:
> Hi Laura,
>
> Thanks for the feedback!
>
> Laura Novich <> writes:
> > If you can't open the document here are my comments
>
> Hmm, attachment got stripped?
>
> > INTRODUCTION
> > ===============
> > 1. Remove The entire first paragraph with the exveption of the first sentence.
> > 2. Replace with - A virtual device in its truest sense is not any different from a physical device. The virtual machine sees a virtual device just as a physical machine would see a physical one. As such, this document will treat virtual devices as physical devices.
>
> This isn't quite correct. Consider:
>
> This document describes the specifications of the “virtio”
> family of devices. These devices are found in virtual
> environments
>
> vs:
> This document describes the specifications of the “virtio”
> family of devices. A virtual device in its truest sense is not
> any different from a physical device.
>
> We need to say that virtio devices are found in virtual environments.
>
> Secondly, you are missing historical context: Xen and HyperV treat
> virtual devices as very different beasts than physical devices. It is
> not a fundamental feature of these devices that they are no different
> from a physical device, but rather a conscious decision by the spec
> authors.
>
> > 3. The purpose of ...
> > 4. replace rather than using boutique to rather than using vendor-specific, per-environment, or per-OS mechanisms.
>
> Is "boutique" too obscure? I like it because it casts an image of the
> alternatives being niche. That may be wishful thinking, but it was a
> deliberate choice :)
>
> > 5. ADD -The categories described above are further defined as follows:
> > Straightforward: Revise last sentence to read - There aren’t any exotic page-flipping or COW mechanisms and it functions as a normal device.[1]
>
> The end of this sentence is not meaningful. Compare:
>
> There is no exotic page-flipping or COW mechanism: it's just
> a normal device.
>
> The ": it's just..." emphasizes the former. With your variant:
>
>
> There aren’t any exotic page-flipping or COW mechanisms and it
> functions as a normal device.
>
> It's not clear what "functions as a normal device" means.
>
> > 6. Efficient: ADD to input and output (I/O),
>
> Again, I disagree. I/O conflates input and output, whereas I wish to
> call them both out separately. Perhaps we should add the word "both",
> ie:
>
> descriptors for both input and output...
>
> > 7. effects from both guest and (not sure but i think you should ADD host) device writing to the same cache
> > lines.
>
> Throughout the document, we explicitly refer to "device" and "driver"
> rather than host and guest. This reinforces the design decision that
> they should appear "normal", as well as being more specific.
>
> > 8. Standard: CHANGE TO READ: Virtio makes no assumptions about the environment in which
> > it operates, beyond what is required in order to allow the bus to attach the host device to the driver on the guest. Virtio
> > devices are implemented over PCI and other buses, and earlier drafts that
> > have been implemented on other buses not included in this specification.[2]
>
> You suggest replacing "beyond supporting the bus attaching the device."
> with "beyond what is required in order to allow the bus to attach the
> host device to the driver on the guest."
>
> What do these extra words add?
>
> There is a missing word "have", but it doesn't need "that".
>
> ...and earlier drafts been implemented on other buses not included
> in this spec.
>
> And I'll accept changing "spec" to "specification".
>
> So this is the difference I have so far from your feedback:
>
> diff --git a/introduction.tex b/introduction.tex
> index 5d57f78..98e1e0d 100644
> --- a/introduction.tex
> +++ b/introduction.tex
> @@ -13,14 +13,14 @@ inter-guest communication) requires copying.
> }
>
> Efficient: Virtio devices consist of rings of descriptors
> - for input and output, which are neatly separated to avoid cache
> + for both input and output, which are neatly separated to avoid cache
> effects from both driver and device writing to the same cache
> lines.
missed this one. I agree.
> Standard: Virtio makes no assumptions about the environment in which
> it operates, beyond supporting the bus attaching the device. Virtio
> devices are implemented over PCI and other buses, and earlier drafts
> - been implemented on other buses not included in this spec.
> + have been implemented on other buses not included in this specification.
> \footnote{The Linux implementation further separates the PCI virtio code
> from the specific virtio drivers: these drivers are shared with
> the non-PCI implementations (currently lguest and S/390).
I tweaked this one a bit more.
Can you pls tell me whether you agree with the patchset I posted?
I think it clarifies misunderstandings (Laura might not be the
only one misreading this text) without losing context.
> Cheers,
> Rusty.
>
>
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