Re: [libvirt] [PATCH 4/4] qemu_capabilities: Temporarily disable dbus-vmstate capability

On Mon, Sep 09, 2019 at 11:23:59AM +0200, Michal Privoznik wrote: >On 9/6/19 5:55 PM, Ján Tomko wrote: >>[cc-ing Marc-André] >> >>On Fri, Sep 06, 2019 at 04:25:19PM +0200, Michal Privoznik wrote: >>>The qemu side is not merged in yet, so there is a chance that the >>>interface will change. Don't detect the capability just yet then. >>> >>>Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; >>>--- >>>src/qemu/qemu_capabilities.c | 1 - >>>1 file changed, 1 deletion(-) >>> >>>diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c >>>index 136999ad0d..7be026ae12 100644 >>>--- a/src/qemu/qemu_capabilities.c >>>+++ b/src/qemu/qemu_capabilities.c >>>@@ -1129,7 +1129,6 @@ struct virQEMUCapsStringFlags >>>virQEMUCapsObjectTypes[] = { >>> { "virtio-serial-pci-non-transitional", >>>QEMU_CAPS_VIRTIO_PCI_TRANSITIONAL }, >>> { "max-x86_64-cpu", QEMU_CAPS_X86_MAX_CPU }, >>> { "bochs-display", QEMU_CAPS_DEVICE_BOCHS_DISPLAY }, >>>- { "dbus-vmstate", QEMU_CAPS_DBUS_VMSTATE }, >>>}; >>> >>>static struct virQEMUCapsStringFlags >>>virQEMUCapsDevicePropsVirtioBalloon[] = { >> >>If >>1) dbus-vmstate is required for migration of a domain using a >>slirp-helper and >>2) we enable this automatically for existing XML configs with >> <interface type='user'/> if >> a) QEMU has QEMU_CAPS_NET_SOCKET_DGRAM >> b) the slirp-helper process is installed on the system >>then we've effectively made their machines unmigratable >> >>So if we want to enable it automatically, we should add: >>c) QEMU has QEMU_CAPS_DBUS_VMSTATE >>regardless of whether dbus-vmstate gets merged into QEMU until libvirt's >>next release > >So are you saying that we should just temporarily revert >QEMU_CAPS_NET_SOCKET_DGRAM detection instead and leave >QEMU_CAPS_DBUS_VMSTATE be? Give that there was a QEMU release which has one but not the other, I'd say permanently revert QEMU_CAPS_NET_SOCKET_DGRAM - even if dbus-vmstate gets merged later, there has been a QEMU release for which we assume one capability and not the other - so libvirt would be starting unmigratable machines. As for QEMU_CAPS_DBUS_VMSTATE, we can either revert it temporarily now or before the libvirt freeze if dbus-vmstate does not get merged by then.

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