Re: Xen ARM small task (WAS: Re: [Xen Question])

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Wed, Nov 23, 2016 at 06:32:41PM +0000, Julien Grall wrote:
> Hi Edgar,
> 
> On 23/11/16 16:38, Edgar E. Iglesias wrote:
> >On Wed, Nov 23, 2016 at 06:26:06PM +0200, Artem Mygaiev wrote:
> >>On 23.11.16 17:19, Julien Grall wrote:
> >>>There is a couple of usecase where we cannot use PV console:
> >>>    - Running unmodified baremetal application as guest. Those
> >>>applications will not have PV driver.
> >>Well, I somehow missed that requirement is to run *unmodified*
> >>applications... I think it will be pretty hard to provide all the HW
> >>infrastructure expected and UARTs as I know them have all possible
> >>issues & workarounds.
> >
> >Hi Artem,
> >
> >The way I see this is not for Xen to provide support for any HW for any
> >platform on all platforms.
> >
> >The way I see it is that on a given platform, for example the ZynqMP.
> >You can run Xen as a partitioning Hypervisor essentially using device
> >passthrough to assign various real HW devices to each VM.
> >
> >The various guests can run unmodified because they each see a subset
> >of the platform.
> >
> >It is useful to have vuarts that go are shared into a single one.
> 
> To expand on the vuart, this is a small emulator to handle write from a
> guest. This was originally designed to handle DOM0 early console that is
> hardcoded on ARM32.
> 
> As mentioned by Artem, read would be more complex as it will mean per-UART
> emulator. IIRC, this would not be a problem for you, right?

Hi Julien,

Right, we wouldn't want to use vuarts for reading.

In our case, I was thinking that guests that need input from serial ports
or that require specific BAUD rates will have to be assigned one of the
UARTs.

For guests that just want to output informative log messages onto the
UART, we can use vuarts.

Best regards,
Edgar

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