On Mon, Jul 01, 2019 at 10:35:17AM +1000, David Gibson wrote:
On Fri, Jun 14, 2019 at 01:45:24PM +0200, Andrea Bolognani wrote:
On Tue, 2019-06-04 at 11:38 +1000, David Gibson wrote:
spapr-vio addresses are used on POWER platform qemu guests, which are based on the PAPR specification. PAPR specifies a number of virtual devices (but not virtio protocol) which are addressed in an abstract namespace.
Currently, libvirt encodes these addresses as 64-bit values. This is not correct: spapr-vio addresses are, and always have been 32-bit. That's true both by the PAPR specification and the qemu implementation.
Therefore, change this in libvirt.
This looks like it would be a breaking change, but it actually isn't. Because these have always been 32-bit at the lower levels, any attempt to use a value here > 0xffffffff would always have failed in any case, this will just make it fail earlier and more clearly.
Thanks for providing this patch, and sorry for taking a while to get back to you about it.
Unfortunately there's one major issue with your approach: even though it's true that a spapr-vio address that can't be represented as a 32-bit value would always have been rejected by QEMU and so the guest would never have been able to start, refusing to parse the value altogether would cause such a guest to disappear completely from libvirt. We don't consider this to be acceptable, because we want to give users a chance to fix their guests that doesn't involve poking at the filesystem behind libvirt's back.
I missed this when it was first posted, but I would have said that we really don't need to consider this scenario. This is a valid thing to worry about *if* the previous config was actually something a person would have used in the past. In this case though there's no way the guest could ever have worked with value > 0xffffffff. At the very most they could have a defined XML config that they might have tried & failed to use. We would have been justified in just changing the parser to use a 32-bit int straight away. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|