Re: [PATCH V2] xen/arm: Initialize acpi_disabled to true during declaration

[Julien Grall <julien@xxxxxxx>]

Hi Oleksandr,

On 25/03/2025 16:05, Oleksandr Tyshchenko wrote:
> > > > Furthermore, what happen if we decide to use ACPI afterwards? Wouldn't
> > > > this mean that the static regions would be reserved even if ACPI doesn't
> > > > use static memory (all the memory is expected to be given to the
> > > > allocator)?
> > > I don't think such hybrid configuration is valid (booting with ACPI yet
> > > declaring reserved regions in DT). See commit:
> > > 9c2bc0f24b2ba7082df408b3c33ec9a86bf20cf0
> > I don't think the commit is preventing hybrid configuration. It is just
> > saying that the region (which could be a static region because this is
> > not supported) will be unreserved.
> >
> > IOW, when booting with Device-Tree you may be able to use static memory.
> > But if you were booting with ACPI, static memory is not supported and
> > therefore the regions should be free for other purpose.
>
> Julien, I see your points, but the current patch does not attempt to
> make static (reserved) memory properly work on ACPI-based system (if it
> is available there), current patch tries to solve the real issue on
> device-tree-based system with Xen compiled with CONFIG_ACPI=y (at least
> unintentionally). 
I am not asking to make ACPI work with static memory. I am asking to not 
break ACPI if the Device-Tree is specifying static memory region.
> However, I wonder, why it has not been noticed so far.
ACPI is not a supported feature and gated by UNSUPPORTED. So the 
implication is you have enabled UNSUPPORTED and anything can happen 
really ;).
> It took some time to understand why just enabling CONFIG_STATIC_MEMORY=y
> triggered a BUG in common code. And it turned out that it was
> CONFIG_ACPI=y in my Xen's .config that caused that consequence (I
> specially wrote so long description to provide full context).
As I wrote above, the only thing I am asking is that memory for static 
regions should be unreserved when ACPI is enabled like it is already the 
case today.
Cheers,

--
Julien Grall