Re: [Qemu-devel] ivshmem property size should be a size, not a string

[Marc-André Lureau]

----- Original Message -----
> Marc-André Lureau <address@hidden> writes:
> 
> > Hi
> >
> > ----- Original Message -----
> >> >
> >> > You can't migrate the peers.
> >> 
> >> Then explain the case N'=0 to me: how can you migrate the master so that
> >> it's connected to a server afterwards?
> >
> > Dest qemu: -incoming.. -chardev socket,path=dest-server
> >
> > That is, start your destination qemu with a destination server. The master
> > origin qemu will migrate the shared memory, and the dest memory will be
> > sync
> > when the migration is done.
> 
> Got it!
> 
> >> > It works fine in the tests. Feel free to point out races or other
> >> > issues.
> >> 
> >> I think I did: doorbell detection is inherently racy.
> >> 
> >> If you think it isn't, please refute my reasoning.
> >
> > I gave you some clues on how I did it in ivshmem-test.c: waiting for a
> > signature on the memory to be mapped (and also checking that peers
> > received ids)
> >
> >> If it's not broken, please explain to me how the guest should find out
> >> whether its ivshmem device sports a doorbell.
> >
> > If you have received ID, you should be good to use the doorbell.
> 
> That's not a complete answer, so let me try a different tack.
> 
> What value will a read of register IVPosition yield
> 
> * if the device has no doorbell:
> 
>   I think the answer is -1.
> 
> * if the device has a doorbell, but it isn't ready, yet:
> 
>   I think the answer is -1.
> 
> * if the device has a doorbell, and it is ready.
> 
>   This is the part you answered already: >= 0.
> 
> Please correct mistakes.
> 

Yes, I think it's correct. Arbitrary informations can be then shared via the 
shared memory (to say whether a doorbell will be present for ex).