Re: [PATCH] arm64: dts: qcom: x1e: bus is 40-bits (fix 64GB models)

[Jonathan Marek]

FYI, for a less hacky solution you can use CONFIG_ARM64_VA_BITS_39, 
arm64 linux as-is refuses to use any memory it can't identity map (and 
the extra 32GB of memory is outside the 39-bit range).

On 11/28/25 5:10 PM, Christopher Obbard wrote:
> Hi,
>
> Sorry to hijack this thread, but I've been carrying this patch to
> workaround the buggy firmware from Stephan for my Lenovo T14s with
> 64gb RAM which seems to make Linux boot & work just fine with
> systemd-boot.
> Of course, it's a hack and not ready for upstream.
>
> On another topic, perhaps we need to add this to
> https://gitlab.com/Linaro/arm64-laptops/linux , what do you think
> Stephan ?
>
> Chris
>
>
> commit 16e21600c6a65ace0c75b5a722e27ced8e1bfc48
> Author: Stephan Gerhold <stephan.gerhold@xxxxxxxxxx>
> Date:   Thu Mar 6 17:41:15 2025 +0000
>
>      HACK: efi-stub: Exclude 40-bit memory
>
> diff --git a/drivers/firmware/efi/libstub/efi-stub.c
> b/drivers/firmware/efi/libstub/efi-stub.c
> index 874f63b4a383..355a9b2c0818 100644
> --- a/drivers/firmware/efi/libstub/efi-stub.c
> +++ b/drivers/firmware/efi/libstub/efi-stub.c
> @@ -106,6 +106,17 @@ efi_status_t
> efi_handle_cmdline(efi_loaded_image_t *image, char **cmdline_ptr)
>   {
>          char *cmdline __free(efi_pool) = NULL;
>          efi_status_t status;
> +       efi_physical_addr_t addr;
> +       unsigned long pages;
> +
> +       addr = 0x0000008800000000;
> +       pages = 0x800000000 / EFI_PAGE_SIZE;
> +       status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
> +                                                EFI_RESERVED_TYPE,
> pages, &addr);
> +       if (status != EFI_SUCCESS) {
> +               efi_err("failed to reserve upper 32 GiB (40-bit memory)\n");
> +               return EFI_OUT_OF_RESOURCES;
> +       }
>
>          /*
>           * Get the command line from EFI, using the LOADED_IMAGE
>
>
>
>
> Cheers!
>
> Chris