On 25/05/20 03:18, Yan Zhao wrote: > On Thu, May 21, 2020 at 04:38:47PM +0200, Paolo Bonzini wrote: >> 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). >> > hi Paolo, > thanks for your reply and never mind :) > > But there's one thing I just can't figure out the reason and eagerly need > your guide. > > why do we have to convert all .write operations to .write_with_attrs and > return MEMTX_ERROR? because of the handling of writes to read-only region?
Not all of them, only those that need to return MEMTX_ERROR. I would like some guidance from Peter as to whether (or when) reads from ROMs should return MEMTX_ERROR. This way, we can use that information to device what the read-only ram-device regions should do. Paolo
