Re: [PATCH] xen/arm: Skip memory nodes if not enabled

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi Luca,

On 26/09/2023 11:52, Luca Fancellu wrote:
> 
> 
>> On 26 Sep 2023, at 06:33, Leo Yan <leo.yan@xxxxxxxxxx> wrote:
>>
>> During the Linux kernel booting, an error is reported by the Xen
>> hypervisor:
>>
>>  (XEN) arch/arm/p2m.c:2202: d0v0: Failing to acquire the MFN 0x1a02dc
>>
>> The kernel attempts to use an invalid memory frame number, which can be
>> converted to: 0x1a02dc << PAGE_SHIFT, resulting in 0x1_a02d_c000.
>>
>> The invalid memory frame falls into a reserved memory node, which is
>> defined in the device tree as below:
>>
>>  reserved-memory {
>>          #address-cells = <0x02>;
>>          #size-cells = <0x02>;
>>          ranges;
>>
>>  ...
>>
>>          ethosn_reserved {
>>                  compatible = "shared-dma-pool";
>>                  reg = <0x01 0xa0000000 0x00 0x20000000>;
>>                  status = "disabled";
>>                  no-map;
>>          };
>>
>>  ...
>>  };
>>
>> Xen excludes all reserved memory regions from the frame management
>> through the dt_unreserved_regions() function. On the other hand, the
>> reserved memory nodes are passed to the Linux kernel. However, the Linux
>> kernel ignores the 'ethosn_reserved' node since its status is
>> "disabled". This leads to the Linux kernel to allocate pages from the
>> reserved memory range.
> 
> I might be wrong, but reading the specifications seems that “status” is not a 
> property
> of the child nodes of /reserved-memory, so I’m not sure Xen should do 
> something about it.
Please take a look at dt documentation (v0.4) for /memory and /reserved-memory.
Under the tables listing possible properties, there is a statement:
Note: All other standard properties (Section 2.3) are allowed but are optional.

"status" is part of standard properties so it is perfectly fine for /memory or 
/reserved-memory
nodes to have it defined.

~Michal