Re: [Xen-devel] [PATCH 02/11] xen/arm: vpl011: Add new hvm params in Xen for ring buffer/event setup

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.03.17 at 12:42, <julien.grall@xxxxxxx> wrote:
> I thought a bit more about those params. I think the name should be 
> generic and not tie to pl011 because we may want to emulate different 
> UART for the guest in the future.

That's reasonable, but I continue to have reservations against the
underlying approach here, namely ...

> Also, by re-using deprecated encoding it means that it will not be 
> possible to use those parameters on x86 if you ever decide to emulate 
> UART in Xen. I am not sure whether if you are happy with that?

... with this in mind: If we wanted to do this for HVM guests, we'd
indeed want the parameters. If we wanted this for PV guests, the
model wouldn't fit at all.

Plus what I'm not understanding (perhaps because most of the
discussion around this seemed to be ARM-specific, and hence I've
skipped reading through it) is - why is this UART emulation needed
in the first place? We've never had a need for such on x86, afaia.

Furthermore - how does this scale? I.e. what if other devices pop
up wanting to be emulated? Or multiple UARTs?

Jan


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