Re: [Qemu-devel] [PATCH 2/4] Add support for execution from ROMs in IO device mode

[Jamie Lokier <jamie@shareable.org>]

Jan Kiszka wrote:
> While IO_MEM_ROMD marks an I/O memory region as "read/execute from RAM,
> but write to I/O handler", there is no flag indicating that an I/O
> region which is fully managed by I/O handlers can still be hosting
> executable code. One use case for this are flash device models that
> switch to I/O mode during reprogramming. Not all reprogramming states
> modify to read data, thus practically allow to continue execution.
> Moreover, we need to avoid switching the modes too frequently for
> performance reasons which requires fetching opcodes while still in I/O
> device mode.

I like this change.

Does "fetching opcodes while still in I/O device mode" fetch opcodes
from the RAM backing, or via the I/O read handlers?

If the latter, I'm wondering how KVM would cope with that.

Thanks,
-- Jamie