Re: [PATCH v3 11/12] xen/riscv: add definition of guest RAM banks

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 4/21/26 12:24 PM, Jan Beulich wrote:
> On 10.04.2026 17:54, Oleksii Kurochko wrote:
> > The dom0less solution uses defined RAM banks as compile-time constants,
> > so introduce macros to describe guest RAM banks.
> >
> > The reason for 2 banks is that there is typically always a use case for
> > low memory under 4 GB, but the bank under 4 GB ends up being small because
> > there are other things under 4 GB it can conflict with (interrupt
> > controller, PCI BARs, etc.). So a second bank is added above that MMIO
> > region (starting at 8 GiB) to provide the remaining RAM; the gap between
> > the two banks also exercises code paths handling discontiguous memory.
> > For Sv32 guests (34-bit GPA, 16 GiB addressable), bank0 provides 2 GB
> > (2–4 GB) and the first 8 GB of bank1 (8–16 GB) is accessible.
> >
> > Extended regions are useful for RISC-V: they could be used to provide a
> > "space" for Linux to map grant mappings.
> >
> > Despite the fact that for every guest MMU mode the GPA could be up
> > to 56 bits wide (except Sv32 whose GPA is 34 bits), the combined size
> > of both banks is limited to 1018 GB as it is more than enough for most
> > use cases.
> >
> > Add inclusion of asm/guest-layout.h to asm/domain.h to make dom0less
> > common code build happy.
> >
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> Again pretty hesitantly:
I suppose beucase of hard-coded layout, right?

> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Thanks.

~ Oleksii