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[Xen-devel] Re: [RFC PATCH] libxl: basic virtio disk / nic configuration

To: Wei Liu <liuw@xxxxxxxxx>
Subject: [Xen-devel] Re: [RFC PATCH] libxl: basic virtio disk / nic configuration support.
From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Date: Thu, 28 Jul 2011 14:05:08 +0100
Cc: Ian, Campbell <Ian.Campbell@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>
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On Thu, 28 Jul 2011, Wei Liu wrote:
> This is a prototype patch for libxl to write virtio disk and nic
> configurations in xenstore.
> I have following questions on this patch:
> 1. VBD encoding for virtio disk.
> In fact, virtio disk driver doesn't care about this encoding, so
> arbitrary number is OK. I also discover a strange bug in xenstore -- if
> I use (2<<28) | (disk<<4) | partition (reserved encoding), it will
> trigger a xenstore parsing bug which affects existing protocol (VIF, VFB
> etc.), causing them fail to initialize frontend and backend.

Apart from the strange bug, I think that the encoding is reasonable.

> 2. Configuration syntax and implementation for virtio disk and nic.
> Currently some hacks are needed to distinguish virtio devices. I hope we
> can get a cleaner implementation.

I think you need to add a new field in libxl_device_disk to specify the
protocol, something like libxl_disk_protocol, that can be:


then parse_disk_config can be modified to distinguish xen disks from
virtio disks and set the field accordingly.

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