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Re: [PATCH v2] xen/dom0less: arm: fix hwdom 1:1 low memory allocation
- To: Julien Grall <julien@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Grygorii Strashko <grygorii_strashko@xxxxxxxx>
- Date: Wed, 6 Aug 2025 11:19:03 +0300
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Denis Mukhin <dmukhin@xxxxxxxx>, Jason Andryuk <jason.andryuk@xxxxxxx>
- Delivery-date: Wed, 06 Aug 2025 08:19:12 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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_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?
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_strashko@xxxxxxxx>
Reviewed-by: Denis Mukhin <dmukhin@xxxxxxxx>
Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
Cheers,
--
Best regards,
-grygorii
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