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

[Julien Grall <julien@xxxxxxx>]

Hi,

On 02/06/2021 11:09, Penny Zheng wrote:
> Hi Julien
>
> > -----Original Message-----
> > From: Julien Grall <julien@xxxxxxx>
> > Sent: Thursday, May 20, 2021 4:51 PM
> > To: Penny Zheng <Penny.Zheng@xxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx;
> > sstabellini@xxxxxxxxxx
> > Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>; Wei Chen
> > <Wei.Chen@xxxxxxx>; nd <nd@xxxxxxx>
> > 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