There are 65 uses of Must/must and 51 uses of MUST in this draft.

Many of the 65 uses of Must/must appear to be normative statements.

Changing a Must or must to uppercase, MUST will trigger an additional public review b/c it changes the conformance requirements of the specification.

Suggest that all uses of Must/must be reviewed at this early stage and modified as appropriate.

Examples:

Under 4.3.1 Basic Concepts, I find:

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The virtio-ccw device acts like a normal channel device, as specified in [S390 PoP] and [S390 Common I/O]. In particular:

• A device must post a unit check with command reject for any command it does not support.
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I am assuming, based on the normative references, that the "must" in the first bullet point should be MUST. Yes? (there are several others in that list)

Under 4.3.2.1.1 Legacy Interfaces: A Note on Setting the Virtio Revision, I find at the end of the first paragraph:

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A transitional driver must operate the device as if it had been able to set revision 0.
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I am assuming you mean that to be MUST, that is it isn't optional, in some cases, etc. but MUST. Yes?

I did not review the MUST instances at all. But I would suggest a close reading just to be sure they are all correct. Certainly all of the must instances should be individually checked.