Hi Julien,

On 06.08.25 00:07, Julien Grall wrote:
Hi Grygorii,

On 05/08/2025 20:00, Grygorii Strashko wrote:
From: Grygorii Strashko <grygorii_stras...@epam.com>

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?

No. I think doc is correct because when regular Dom0(hwdom)(initial domain)
is created code goes through regular Dom0 path and "dom0_mem" is accounted for.

create_dom0()->construct_dom0()
      kinfo.unassigned_mem = dom0_mem;
      construct_hwdom()->allocate_memory_11()

The issue happens in dom0less mode when hwdom is created and domain's 
configuration parameters
are obtained from DT.


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

Right, it should be "which has"

memory size in both cases: regular dom0 boot and dom0less boot.

Fixes: 52cb53f1816a ("xen/arm: dom0less hwdom construction")
Signed-off-by: Grygorii Strashko <grygorii_stras...@epam.com>
Reviewed-by: Denis Mukhin <dmuk...@ford.com>
Reviewed-by: Jason Andryuk <jason.andr...@amd.com>

Acked-by: Julien Grall <jgr...@amazon.com>

Cheers,


--
Best regards,
-grygorii


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