linux-kernel - Re: [PATCH v1] KVM: s390: use defines for execution controls

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Date:   Tue, 14 Mar 2017 14:51:50 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     David Hildenbrand <david@...hat.com>, kvm@...r.kernel.org
Cc:     Cornelia Huck <cornelia.huck@...ibm.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] KVM: s390: use defines for execution controls

On 03/13/2017 11:48 AM, David Hildenbrand wrote:
> Let's replace the bitmasks by defines. Reconstructed from code, comments
> and commit messages.
> 
> Tried to keep the defines short and map them to feature names. In case
> they don't completely map to features, keep them in the stye of ICTL
> defines.
> 
> This effectively drops all "U" from the existing numbers. I think this
> should be fine (as similarly done for e.g. ICTL defines).

The patch does change the binary result and this seems to be related to the
U removal. But as far as I can tell this is fine, its just some subtle 
undefined behaviour change between unsigned/signed which we do not care
about.

> 
> I am not 100% sure about the ECA_MVPGI and ECA_PROTEXCI bits as they are
> always used in pairs.

Just historic baggage, e.g. in 3.10 we set eca to 0xC1002001 and over
time we split those out piece by piece. Those two are just the last men 
standing.

I think I am going to apply this with some minor changes (EC* names). Ok
when I do the changes?