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

[Peter Maydell]

On Mon, 25 May 2020 at 11:20, Paolo Bonzini <address@hidden> wrote:
> 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.

In general I think writes to ROMs (and indeed reads from ROMs) should
not return MEMTX_ERROR. I think that in real hardware you could have
a ROM that behaved either way; so our default behaviour should probably
be to do what we've always done and not report a MEMTX_ERROR. (If we
needed to I suppose we should implement a MEMTX_ERROR-reporting ROM,
but to be honest there aren't really many real ROMs in systems these
days: it's more often flash, whose response to writes is defined
by the spec and is I think to ignore writes which aren't the
magic "shift to program-the-flash-mode" sequence.)

thanks
-- PMM