Re: [RFC PATCH 2/5] system/memory: support unaligned access

[Peter Maydell]

On Fri, 6 Dec 2024 at 16:43, Peter Xu <peterx@redhat.com> wrote:
> I assume it's about xhci_cap_ops then.  If you agree we can also mention
> xhci_cap_ops when dscribing it, so readers can easily reference the MR
> attributes from the code alongside with understanding the use case.
>
> Does it mean that it could also work if xhci_cap_ops.impl.min_access_size
> can be changed to 2 (together with additional xhci_cap_read/write support)?
>
> Note that I'm not saying it must do so even if it would work for xHCI, but
> if the memory API change is only for one device, then it can still be
> discussed about which option would be better on changing the device or the
> core.

I think the memory system core has been broken in this area
for a long time -- it purports to support impls which only
do a subset of what the valid operations are, but it actually
does buggy and wrong things in some cases. So far
we have effectively worked around it by avoiding defining
MemoryRegionOps that try to use the buggy areas, but I
think it's much better to fix the code so it really does
what it's theoretically intended to do.

thanks
-- PMM