Re: [PATCH 01/10] xen/arm: introduce domain on Static Allocation

[Julien Grall <julien@xen.org>]

Hi,

On 02/06/2021 11:09, Penny Zheng wrote:
> Hi Julien
> 
>> -----Original Message-----
>> From: Julien Grall <julien@xen.org>
>> Sent: Thursday, May 20, 2021 4:51 PM
>> To: Penny Zheng <Penny.Zheng@arm.com>; xen-devel@lists.xenproject.org;
>> sstabellini@kernel.org
>> Cc: Bertrand Marquis <Bertrand.Marquis@arm.com>; Wei Chen
>> <Wei.Chen@arm.com>; nd <nd@arm.com>
>> Subject: Re: [PATCH 01/10] xen/arm: introduce domain on Static Allocation
>>
>> Hi,
>>
>> On 20/05/2021 07:07, Penny Zheng wrote:
>>>>> It will be consistent with the ones defined in the parent node, domUx.
>>>> Hmmm... To take the example you provided, the parent would be chosen.
>>>> However, from the example, I would expect the property #{address,
>>>> size}-cells in domU1 to be used. What did I miss?
>>>>
>>>
>>> Yeah, the property #{address, size}-cells in domU1 will be used. And
>>> the parent node will be domU1.
>>
>> You may have misunderstood what I meant. "domU1" is the node that
>> contains the property "xen,static-mem". The parent node would be the one
>> above (in our case "chosen").
>>
> 
> I re-re-reconsider what you meant here, hope this time I get what you mean, correct me if I'm wrong,
> List an example here:
> 
>      / {
>          reserved-memory {
>              #address-cells = <2>;
>              #size-cells = <2>;
> 
>              staticmemdomU1: static-memory@0x30000000 {
>                  compatible = "xen,static-memory-domain";
>                  reg = <0x0 0x30000000 0x0 0x20000000>;
>              };
>          };
> 
>          chosen {
>              domU1 {
>                  compatible = "xen,domain";
>                  #address-cells = <0x1>;
>                  #size-cells = <0x1>;
>                  cpus = <2>;
>                  xen,static-mem = <&staticmemdomU1>;
> 
>                 ...
>              };
>          };
>      };
> 
> If user gives two different #address-cells and #size-cells in reserved-memory and domU1, Then when parsing it
> through `xen,static-mem`, it may have unexpected answers.

Why are you using the #address-cells and #size-cells from the node domU1 
to parse staticmemdomU1?

> I could not think a way to fix it properly in codes, do you have any suggestion? Or we just put a warning in doc/commits.

The correct approach is to find the parent of staticmemdomU1 (i.e. 
reserved-memory) and use the #address-cells and #size-cells from there.

Cheers,

-- 
Julien Grall