Re: [PATCH v6 1/3] memory: drop guest writes to read-only ram device regions

[Paolo Bonzini]

On 30/04/20 11:40, Peter Maydell wrote:
>> This does not "drop" a write to a r/o region -- it causes it to generate
>> whatever the guest architecture's equivalent of a bus error is (eg data
>> abort on Arm).


> More generally, this change seems a bit odd: currently we do not
> check the mr->readonly flag here, but in general guests don't get
> to write to ROM areas. Where is that check currently done

Writes to ROM are directed to mr->ops unassigned_mem_ops.  Because _all_
ram-device reads and writes go through the ops, for ram-device we have
to stick the check for mr->readonly in the ops.

On one hand, I was quite surprised to see that unassigned_mem_write does
not return MEMTX_ERROR now that I looked at it.

On the other hand, we should use MEMTX_ERROR in patch 2 as well, if we
decide it's the way to go.

(Sorry Yan for the late response).

Paolo