Re: [Qemu-devel] [PATCH 0/5] pc: make ROMs resizeable

[Markus Armbruster]

"Michael S. Tsirkin" <address@hidden> writes:

> On Tue, Nov 18, 2014 at 03:47:16PM +0100, Markus Armbruster wrote:
>> "Michael S. Tsirkin" <address@hidden> writes:
>> 
>> > At the moment we migrate ROMs which reside in fw cfg, which allows
>> > changing ROM code at will, and supports migrating largish blocks early,
>> > with good performance.
>> > However, we are running into a problem: changing size breaks
>> > migration every time.
>> 
>> Pardon my ignorance... changing ROM in migration?  I would expect
>> migration to be as transparent for ROM as it is for RAM.  What am I
>> missing?
>> 
>> [...]
>
> Nothing really.
>
> We migrate RAM size too - but if there's a mismatch, migration fails.
>
> RAM size is user configurable.
>
> ROM is used internally so we have to figure out the size,
> and it turned out to be a hard problem, so we end up maintaining
> logic for ROM size "like we did in 1.7" "like we did in 2.0" etc.
>
> I don't want to add any more: let's just accept whatever is migrated,
> and stick to it.

Are you proposing to change ROM size on the target from "whatever was
configured during startup" to "whatever is configured on the source"?