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Re: [PATCH RFC 0/3] xen: add hypfs per-domain abi-features





On 10/12/2020 07:49, Jürgen Groß wrote:
On 09.12.20 17:24, Julien Grall wrote:
Hi,

On 09/12/2020 16:16, Juergen Gross wrote:
This small series is meant as an example how to add further dynamical
directories to hypfs. It can be used to replace Paul's current approach
to specify ABI-features via domain create flags and replace those by
hypfs nodes.

This can only work if all the ABI-features are not required at the time of creating the domain.

Yes. In case there is some further initialization needed this has to be
done later depending on the setting.
We used to allocate vCPUs after the domain has been created. But this ended up in a can of worms because this requires a careful ordering of the hypercalls.

So I would rather like to avoid introducing similar operation again...


Those features should also be set only once. Furthermore, HYPFS is so far meant to be optional.

"set once" isn't the point. They should not be able to change after the
domain has been started, and that is covered.

That really depends on the flag. Imagine there are dependencies between flags or memory needs to be allocated.



So it feels to me Paul's approach is leaner and better for the ABI-features purpose.

Depends.

My approach doesn't need any tools side changes after first
implementation when adding new abi-features. And it isn't expanding an
unstable interface.

In the end this is the reason I marked this series as RFC. If using
flags is preferred, fine.

I prefer the flag version. Let see what other thinks.

Cheers,

---
Julien Grall



 


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