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Re: [PATCH] libs/light: pass some infos to qemu
- To: Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Mon, 18 Jan 2021 10:07:22 +0100
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- Cc: <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>
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On Mon, Jan 18, 2021 at 09:52:14AM +0100, Manuel Bouyer wrote:
> On Mon, Jan 18, 2021 at 09:36:42AM +0100, Roger Pau Monné wrote:
> > I also wonder why NetBSD needs to add the tap interface to the bridge
> > in the QEMU script instead of doing it from the hotplug script called
> > by libxl, like Linux and FreeBSD do.
>
> the tap interface is created by qemu itself, its name is not known outside
> of qemu. Also, is there guarantee that qemu has created the tap before
> the hotplug script is called ?
Yes, the toolstack will wait for QEMU to be initialized at which point
the tap interface has been created.
I think I remember now why this didn't work on NetBSD. We ask QEMU to
create the tap interface with a specific name (using the vifname=
parameter), but NetBSD doesn't have the ioctl to rename network
interfaces implemented, and thus cannot rename the interface from tapX
to vifX.Y-emu, and hence you need to use the QEMU script from QEMU
itself because it's the only entity that knows the name of the tap
interface created.
If you agree, can you add something along the lines to the commit
message? So that we remember why NetBSD needs to use the QEMU scripts.
Thanks, Roger.
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