Re: [PATCH 10/12] xen/arm: if is_domain_direct_mapped use native UART address for vPL011

[Julien Grall <julien@xxxxxxx>]

On 01/05/2020 02:26, Stefano Stabellini wrote:
> On Wed, 15 Apr 2020, Julien Grall wrote:
> > Hi Stefano,
> >
> > On 15/04/2020 02:02, Stefano Stabellini wrote:
> > > We always use a fix address to map the vPL011 to domains. The address
> > > could be a problem for domains that are directly mapped.
> > >
> > > Instead, for domains that are directly mapped, reuse the address of the
> > > physical UART on the platform to avoid potential clashes.
> > How do you know the physical UART MMIO region is big enough to fit the PL011?
> That cannot be because the vPL011 MMIO size is 1 page, which is the
> minimum right?
No, there are platforms out with multiple UARTs in the same page (see 
sunxi for instance).
> > What if the user want to assign the physical UART to the domain + the vpl011?
> A user can assign a UART to the domain, but it cannot assign the UART
> used by Xen (DTUART), which is the one we are using here to get the
> physical information.
>
>
> (If there is no UART used by Xen then we'll fall back to the virtual
> addresses. If they conflict we return error and let the user fix the
> configuration.)
If there is no UART in Xen, how the user will know the addresses 
conflicted? Earlyprintk?
Cheers,

--
Julien Grall