Re: [PATCH v4 2/2] xen/arm: Enlarge identity map space to 10TB

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi,

On 13/10/2023 14:26, Leo Yan wrote:
> 
> 
> On ADLink AVA platform (Ampere Altra SoC with 32 Arm Neoverse N1 cores),
> the physical memory regions are:
> 
>   DRAM memory regions:
>     Node[0] Region[0]: 0x000080000000 - 0x0000ffffffff
>     Node[0] Region[1]: 0x080000000000 - 0x08007fffffff
>     Node[0] Region[2]: 0x080100000000 - 0x0807ffffffff
> 
> The UEFI loads Xen hypervisor and DTB into the high memory, the kernel
> and ramdisk images are loaded into the low memory space:
> 
>   (XEN) MODULE[0]: 00000807f6df0000 - 00000807f6f3e000 Xen
>   (XEN) MODULE[1]: 00000807f8054000 - 00000807f8056000 Device Tree
>   (XEN) MODULE[2]: 00000000fa834000 - 00000000fc5de1d5 Ramdisk
>   (XEN) MODULE[3]: 00000000fc5df000 - 00000000ffb3f810 Kernel
> 
> In this case, the Xen binary is loaded above 8TB, which exceeds the
> maximum supported identity map space of 2TB in Xen. Consequently, the
> system fails to boot.
> 
> This patch enlarges identity map space to 10TB, allowing module loading
> within the range of [0x0 .. 0x000009ff_ffff_ffff].
> 
> Fixes: 1c78d76b67 ("xen/arm64: mm: Introduce helpers to 
> prepare/enable/disable")
I don't think a fixes tag applies here given that 2TB was just a number we 
believed is enough
and all of this is platform dependent. This can be dropped on commit if 
committer agrees.

> Reported-by: Alexey Klimov <alexey.klimov@xxxxxxxxxx>
> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>

~Michal