On Mon, 4 Jun 2018 16:17:52 +0200 Ján Tomko <jtomko@xxxxxxxxxx> wrote: > On Mon, Jun 04, 2018 at 02:05:17PM +0800, Yi Min Zhao wrote: > > > > > >在 2018/6/2 下午10:18, Ján Tomko 写道: > >> On Thu, May 24, 2018 at 02:24:30PM +0200, Xiao Feng Ren wrote: > >>> From: Yi Min Zhao <zyimin@xxxxxxxxxxxxx> > >>> > >>> The pci-root depends on zpci capability. So autogenerate pci-root if > >>> zpci exists. > >>> > >>> Signed-off-by: Yi Min Zhao <zyimin@xxxxxxxxxxxxx> > >>> Reviewed-by: Boris Fiuczynski <fiuczy@xxxxxxxxxxxxxxxxxx> > >>> Reviewed-by: Stefan Zimmermann <stzi@xxxxxxxxxxxxx> > >>> Reviewed-by: Bjoern Walk <bwalk@xxxxxxxxxxxxxxxxxx> > >>> --- > >>> src/qemu/qemu_domain.c | 1 + > >>> 1 file changed, 1 insertion(+) > >>> > >>> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c > >>> index ee676a2789..05136540aa 100644 > >>> --- a/src/qemu/qemu_domain.c > >>> +++ b/src/qemu/qemu_domain.c > >>> @@ -3068,6 +3068,7 @@ qemuDomainDefAddDefaultDevices(virDomainDefPtr > >>> def, > >>> case VIR_ARCH_S390X: > >>> addDefaultUSB = false; > >>> addPanicDevice = true; > >>> + addPCIRoot = virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_ZPCI); > >> > >> So from a certain QEMU version all the S390 machine types have an > >> implicit PCI root? > >If zPCI exists, there must be pci root. > >> > >> Is migration a thing on S390? > >I'm not clear with your said. Could you please explain more? > >> > > Well from this code it seems from a certain version, QEMU added a new > implicit device for all machine types, without letting libvirt have > control over it, which is strange. > > So if we have a machine started by older libvirt on older QEMU, > can we do a live migration to a newer libvirt+QEMU with the zPCI > functionality? Or did live migration never work on S390? [warning, perspective of a non-libvirt qemu developer ahead] Sadly, zpci support in qemu took quite some time from "we've committed a prototype that works for some of us with hacked-up setups" to "should be usable". - The s390 phb device has been created unconditionally since 2.3. We tried to make it conditional later, but could not find a way to do so without breaking migration. - Compat machines for s390 only go back to 2.4, so this hopefully should not hurt migration. - The zpci device (which seems to be what the zpci capability refers to, if I read patch 2 correctly) has only existed since 2.7, so any qemu supporting the zpci device also has the s390 phb present, which seems to be in line with what this patch does. - You'll also need the zpci cpu feature bit set to have something that is actually usable by a guest. That was added in 2.10. -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
