Re: Keystone Issue

[Julien Grall <julien@xxxxxxx>]

On 04/06/2020 09:02, Bertrand Marquis wrote:
> Hi,
Hi Bertrand,

> > On 3 Jun 2020, at 19:09, Julien Grall <julien@xxxxxxx> wrote:
> >
> >
> >
> > On 03/06/2020 18:13, CodeWiz2280 wrote:
> > > Hi Julien,
> > Hello,
> >
> > In general, we avoid top post on xen-devel, instead we reply inline. I believe 
> > gmail should allow you to do it :).
> >
> > > The offset is already applied to the memory nodes in the device tree, meaning a 
> > > direct Linux boot from uboot would have only the 36-bit addresses in the device 
> > > tree (0x8_0000_0000 and 0x8_8000_0000).  Linux would start executing from a 
> > > 32-bit address space however and then switch over to the aliased 36-bit 
> > > addresses in the device tree as discussed below by early_paging_init().
> > > I had to add the 32-bit memory node 0x8000_0000 in uboot in place of the 0x8_0000_0000 
> > > node otherwise Xen would detect the 32-bit processor and panic on "Unable to detect 
> > > the first memory bank" in domain_build.c.
> > So for 32-bit Xen requires to have the first bank below 4GB. This is because 
> > you can't boot from a physical address above 32-bit.
> >
> > Obviously, this check wouldn't work on your platform because all your memory 
> > will be above 4GB.
> I think that the Keystone board has low memory accessible at 2 different 
> address (one low and one high).
>
> I would here suggest to have a dtb with 2 regions (one under 4GB and one over) 
> and remove from the region over 4G the area already addressed by the region 
> under 4GB.
I thought about this. However, in an earlier reply, David wrote:

"4. The dom0 kernel will boot from xen if the early_paging_init switch 
step is skipped, and the low mem stays in 32-bit....but there is a
problem with the peripherals so this is not an acceptable solution."

It is not clear to me what sort of issues will arise with the 
peripherals. But I have assumed that it wouldn't be possible for Dom0 to 
keep using the memory below 4GB.
Cheers,

--
Julien Grall