On 06/24/2014 03:15 PM, Paolo Bonzini wrote: > Il 23/06/2014 23:35, Alexey Kardashevskiy ha scritto: >> nec-usb-xhci is off for PC_COMPAT_1_3 because of what? PIIX emulation was >> broken in 1.3? Or nec-usb-xhci? > > nec-usb-xhci is not "off".
Yes, my bad, I understood (but explained this wrong) that XHCI is enabled but without MSI. > > .driver = "nec-usb-xhci",\ > .property = "msi",\ > .value = "off",\ > > What's off is MSI (and MSI-X), because it wasn't implemented. > >> If it is the latter, why is the tweak limited by PC? > > Because at the time nobody cared about migration compatibility (even now > only pSeries is starting to care). "only pSeries"? There are plenty of x86 machines already and if it is not for migration support, then what are they all for? :) >> Looks like I must copy PC_COMPAT_X_X as PSERIES_COMPAT_X_X starting 1.6 (or >> 1.7 - whichever starts supporting migration well enough on pseries) because >> pretty much of what they do is tweaking PCI devices and we can have all of >> these devices on pseries. > > It's not necessary to do this retroactively, unless you're planning to test > forward migration from 1.6 to 2.1. Just start with 2.2 (and add > pseries-2.1 now as an alias). > > Note that firmware interfaces and CPU features should also be versioned if > they're guest visible. That's the point of functions like pc_compat_1_6. > >> And then keep an eye on what is happening in PC >> world to copy same tweaks to pseries as they come. Is that correct? > > Yes. We should come up sooner or later with a way to share the tweaks though. > >> Others (ARM, s390) do not do that because they do not support PCI? Or >> migration? Or some other reason? > > This is not limited to PCI. Others do not support migration across > different QEMU versions. Yeah, I got that now. Thanks! -- Alexey