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Re: [PATCH v2] xen/arm: Convert runstate address during hypcall

Hi Jan,

On 31/07/2020 07:39, Jan Beulich wrote:
We're fixing other issues without breaking the ABI. Where's the
problem of backporting the kernel side change (which I anticipate
to not be overly involved)?
This means you can't take advantage of the runstage on existing Linux without any modification.

If the plan remains to be to make an ABI breaking change,

For a theoritical PoV, this is a ABI breakage. However, I fail to see how the restrictions added would affect OSes at least on Arm.

In particular, you can't change the VA -> PA on Arm without going through an invalid mapping. So I wouldn't expect this to happen for the runstate.

The only part that *may* be an issue is if the guest is registering the runstate with an initially invalid VA. Although, I have yet to see that in practice. Maybe you know?

 then I
think this will need an explicit vote.

I was under the impression that the two Arm maintainers (Stefano and I) already agreed with the approach here. Therefore, given the ABI breakage is only affecting Arm, why would we need a vote?


Julien Grall



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