Re: [PATCH v2] xen/dom0less: arm: fix hwdom 1:1 low memory allocation

[Julien Grall <julien@xxxxxxx>]

Hi Grygorii,

On 05/08/2025 20:00, Grygorii Strashko wrote:
> From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
>
> Call stack for dom0less hwdom case (1:1) memory:
> create_domUs
> |-construct_domU
>    |-construct_hwdom()
>      |-allocate_memory_11()
>
> And allocate_memory_11() uses "dom0_mem" as:
> min_low_order =
>    get_order_from_bytes(min_t(paddr_t, dom0_mem, MB(128)));
>
> In case of dom0less boot the "dom0_mem" is not used and defaulted to 0,
From docs/mics/xen-command-linux.pandoc:

---

### dom0_mem (ARM)
> `= <size>`

Set the amount of memory for the initial domain (dom0). It must be
greater than zero. This parameter is required.

---

If dom0_mem is effectively optional, then shouldn't the doc be updated?

> which causes min_low_order to get high value > order and so no allocations
> happens from low memory.
> > Fix it, by using kinfo->unassigned_mem instead of "dom0_mem" has 
correct
> memory size in both cases: regular dom0 boot and dom0less boot.
>
> Fixes: 52cb53f1816a ("xen/arm: dom0less hwdom construction")
> Signed-off-by: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
> Reviewed-by: Denis Mukhin <dmukhin@xxxxxxxx>
> Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

--
Julien Grall