Re: [PATCH v1 5/5] xen/riscv: map FDT

[Julien Grall <julien@xxxxxxx>]

Hi,

On 11/07/2024 12:28, Oleksii wrote:
> Add Julien as he asked basically the same question in another thread.
Thanks!

> On Thu, 2024-07-11 at 12:50 +0200, Jan Beulich wrote:
> > On 11.07.2024 12:26, Oleksii wrote:
> > > On Thu, 2024-07-11 at 11:54 +0200, Jan Beulich wrote:
> > > > On 11.07.2024 11:40, Oleksii wrote:
> > > > > On Wed, 2024-07-10 at 14:38 +0200, Jan Beulich wrote:
> > > > > > On 03.07.2024 12:42, Oleksii Kurochko wrote:
> > > Does it make sense now?
> > I think so, yet at the same time it only changes the question: Why is
> > it
> > that you absolutely need to use setup_initial_mapping()?
> There is no strict requirement to use setup_initial_mapping(). That
> function is available to me at the moment, and I haven't found a better
> option other than reusing what I currently have.
I am not very familiar with the code base for RISC-V, but looking at the 
context in the patch, it seems you will still have the identity mapping 
mapped until start_xen().
I assume we don't exactly know where the loader will put Xen in memory. 
Which means that the region may clash with your defined runtime regions 
(such as the FDT). Did I misunderstand anything?
That's one of the reason on Arm we are trying to enable the MMU very 
early. The only thing we setup is a mapping for Xen (and earlyprintk) 
all the rest will be mapped once the MMU is on.
With that, the only thing you need to take care off the runtime Xen 
address overlapping with the identity mapping.
Cheers,

--
Julien Grall