Re: [PATCH v2 1/2] docs: update hyperlaunch device tree

[Michal Orzel <michal.orzel@xxxxxxx>]

Hi Daniel,

On 03/08/2023 18:57, Daniel P. Smith wrote:
> 
> 
> On 8/3/23 07:45, Michal Orzel wrote:
>> Hi Daniel,
>>
>> On 03/08/2023 12:44, Daniel P. Smith wrote:
>>>
>>>
>>> With on going development of hyperlaunch, changes to the device tree 
>>> definitions
>>> has been necessary. This commit updates the specification for all current 
>>> changes
>>> along with changes expected to be made in finalizing the capability.
>>>
>>> This commit also adds a HYPERLAUNCH section to the MAINTAINERS file and 
>>> places
>>> this documentation under its purview. It also reserves the path
>>> `xen/common/domain-builder` for the hyperlaunch domain builder code base.
>>>
>>> Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>

[...]
>>> +
>>>   memory
>>> -  The amount of memory to assign to the domain, in KBs.
>>> +  The amount of memory to assign to the domain, in KBs. This field uses a 
>>> DTB
>>> +  Reg which contains a start and size. For memory allocation start may or 
>>> may
>>> +  not have significance but size will always be used for the amount of 
>>> memory
>>>     Required.
>>>
>>> +  Format: String  min:<sz> | max:<sz> | <sz>, e.g. "256M"
>> There is a mismatch between the description and above format:
>> - KB vs MB
>> - string vs reg format
>> - the x86 example uses string and Arm uses reg format
> 
> Hmmm. I missed this in the hyperlaunch v1 update. In the original design
> that came from the working group it was going to use a reg as suggest by
> dom0less. During development of v1, we found it was not rich enough to
> express how Dom0 could be allocated memory and switched to a string to
> mirror the dom0 memory hypervisor command line parameter.
On Arm, dom0_mem cmdline parameter is used to specify only size (no min,max)

> 
> A question for those involved with dom0less, is what are the opinions
> about using this form for memory allocation. Is it required/possible to
> be able to instruct the hypervisor what physical address to use as the
> start of a domain's memory?
"memory" dt property is used to specify just amount of memory for domain in KBs 
using reg format.
It is not used to specify the static memory region (with start and size). For 
that, we have another property called "xen,static-mem".
Therefore, it would be possible to switch memory to string but it would not be 
compatible with the current use anymore.

~Michal