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


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;
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


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.


Julien Grall



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