On 12 November 2018 at 17:38, Dr. David Alan Gilbert <dgilb...@redhat.com> wrote: > * Peter Maydell (peter.mayd...@linaro.org) wrote: >> That would require us to support backing it properly with a block >> device, like the pflash flash devices, I think. (This would >> be the long term way to be able to dump the pointer property, >> in favour of a block backend property.) > > There's a number of separate questions: > > a) Can the guest write to the EEPROM or are we just treating it as a > ROM? > b) If a guest writes to the EEPROM and then resets does the data stay > there [I'd expect so, it's an EEPROM] > c) It the guest writes to the EEPROM and then quits qemu and restarts > does the data stay there? > d) If the guest is migrated does it keep the data it's written - I'd say > it must because otherwise it would get confused. > > (c) is where it starts looking like a pflash - which does get a bit > messy.
My view is that the answers to b and c should always be the same: resetting QEMU with a system reset should look the same as if you stopped QEMU and restarted it. (Our only kind of system reset is an emulation of a hard powercycle.) In this case, the answer to "a" is currently "yes, it can write to it", though whether any guest takes advantage of that is a different question. thanks -- PMM
