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

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

> On 26 Sep 2023, at 11:04, Michal Orzel <michal.orzel@xxxxxxx> wrote:
> 
> 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.

Thanks for pointing that out, I missed that bit.

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