Re: [PATCH v3 0/2] hw/arm/raspi4b: fix guest RAM capped at ~1 GiB regardless of machine size

On Tue, 11 Aug 2026 at 15:35, Marcelo Manzo <[email protected]> wrote:
>
> While working on unrelated raspi4b issues, I noticed the guest never
> seemed to have as much RAM as I'd given it and tracked it down to
> hw/arm/raspi4b.c's raspi4_modify_dtb(): it decides whether to add a
> second memory node above the 1 GiB peripheral hole by checking
> info->ram_size, but that field is the boot loader's RAM budget for
> where it's allowed to place the kernel/initrd/dtb image, itself always
> capped to at most UPPER_RAM_BASE - vcram_size by
> raspi_base_machine_init(). Since that capped value can never exceed
> UPPER_RAM_BASE by construction, the condition was never true for any
> raspi4b configuration -- the second node was never added, and the
> guest never saw more than ~1 GiB of RAM regardless of the machine's
> nominal size. board_ram_size(info->board_id), computed one line above
> in the same function, is the value that was actually needed.
>
> Patch 1 fixes it (one line); patch 2 adds a regression test.
>



Applied to target-arm.next, thanks.

-- PMM