Re: [PATCH v1 6/6] xen/riscv: enable DOMAIN_BUILD_HELPERS

[Oleksii Kurochko <oleksii.kurochko@gmail.com>]

On 2/13/26 2:11 PM, Jan Beulich wrote:
>>>> +#define GUEST_RAM0_BASE   xen_mk_ullong(0x80000000) /* 2GB of low RAM @ 2GB */
>>>> +#define GUEST_RAM0_SIZE   xen_mk_ullong(0x80000000)
>>>> +
>>>> +#define GUEST_RAM_BANK_BASES   { GUEST_RAM0_BASE }
>>>> +#define GUEST_RAM_BANK_SIZES   { GUEST_RAM0_SIZE }

(cut)

> If all you want are 2Gb guests, why would such guests be 64-bit? And with
> (iirc) RV32 permitting more than 4Gb (via PPN being 22 bits wide), perhaps
> even a 32-bit hypervisor would suffice?

Btw, shouldn't we look at VPN width?

My understanding is that we should take GUEST_RAM0_BASE as sgfn address
and then map it to mfn's page (allocated by alloc_domheap_pages())? And then
repeat this process until we won't map GUEST_RAM0_SIZE.

In this case for RV32 VPN (which is GFN in the current context) is 32-bit
wide as RV32 supports only Sv32, what is 2^32 - 1, what is almost 4gb.

~ Oleksii