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SubjectRe: [PATCH RFC] virtio-spec: flexible configuration layout
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On Wed, 2011-11-09 at 12:18 +0200, Michael S. Tsirkin wrote:
> On Wed, Nov 09, 2011 at 11:55:02AM +0200, Sasha Levin wrote:
> > On Tue, 2011-11-08 at 23:40 +0200, Michael S. Tsirkin wrote:
> > > Here's a spec change documenting what my C patch does
> > > (almost - I tweaked the layout a bit, but the idea is the same).
> > > Some more cleanups are needed but I thought I'd send it
> > > for early flames/comments.
> > >
> > > The idea is simple: we split functionally unrelated
> > > register groups to independent structures, and let
> > > the device place is anywhere using a capability
> > > in PCI configuration space.
> >
> > I'm also wondering it it's ok to move virtio configuration out of virtio
> > space and into PCI space for archs that don't have PCI (such as ARM).
>
> A bit of confusion here: no register is moved from memory into
> configuration space. Configuration space only gains a list of
> pointers into memory/pio space.

The definition of the way the virtio configuration space looks is moved
into PCI configuration space, it was constant before.

> > Would it mean they get stuck with legacy configuration (and no new
> > features)? Or is there an alternative for them?
>
> The change only affects the layout of virtio PCI. Arches that don't
> have PCI don't use virtio PCI, presumably?
>
> BTW, the spec only covers x86 ATM, this needs to be fixed.

From what I see there is a WIP by Pawel Moll <pawel.moll@arm.com> to add
virtio platform drivers which get virtio working on ARM for example, and
by Peter Maydell <peter.maydell@linaro.org> to modify the spec to
support MMIO access (besides PCI).

Maybe worth seeing if it works for them...

--

Sasha.



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