Am 15.05.23 um 10:32 schrieb Juan Quintela: > When we detect that we have broken backwards compantibility in a
compatibility (...) > + > +In qemu-8.0 we got this commit: :: > + > + commit 9a6ef182c03eaa138bae553f0fbb5a123bef9a53 > + Author: Jonathan Cameron <jonathan.came...@huawei.com> > + Date: Thu Mar 2 13:37:03 2023 +0000 > + > + hw/pci/aer: Add missing routing for AER errors > + > +The relevant bits of the commit for our example are this ones: > + > + --- a/hw/pci/pcie_aer.c > + +++ b/hw/pci/pcie_aer.c > + @@ -112,6 +112,10 @@ int pcie_aer_init(PCIDevice *dev, > + > + pci_set_long(dev->w1cmask + offset + PCI_ERR_UNCOR_STATUS, > + PCI_ERR_UNC_SUPPORTED); > + + pci_set_long(dev->config + offset + PCI_ERR_UNCOR_MASK, > + + PCI_ERR_UNC_MASK_DEFAULT); > + + pci_set_long(dev->wmask + offset + PCI_ERR_UNCOR_MASK, > + + PCI_ERR_UNC_SUPPORTED); > + > + pci_set_long(dev->config + offset + PCI_ERR_UNCOR_SEVER, > + PCI_ERR_UNC_SEVERITY_DEFAULT); > + These changes are not part of commit 9a6ef182c0 ("hw/pci/aer: Add missing routing for AER errors") but rather the one before it, namely 010746ae1d ("hw/pci/aer: Implement PCI_ERR_UNCOR_MASK register") > +The patch changes how we configure pci space for AER. But qemu fails Should QEMU and PCI be capitalized in the text parts? > +when the pci space configuration is different betwwen source and between > +destination. > + > +The following commit show how this got fixed: shows (...) > + > +So the normality has been restaured and everything is ok, no? restored > + > +Not really, now our matrix is much bigger. We started with the easy > +cases, migration from the same version to the same version always > +works: > + > +- $ qemu-7.2 -M pc-7.2 -> qemu-7.2 -M pc-7.2 > +- $ qemu-8.0 -M pc-7.2 -> qemu-8.0 -M pc-7.2 > +- $ qemu-8.0.1 -M pc-7.2 -> qemu-8.0.1 -M pc-7.2 > + > +Now the interesting ones. When the QEMU processes versions are > +different. For the 1st set, their fail and we can do nothing, both > +versions are relased and we can't change anything. released > + > +- $ qemu-7.2 -M pc-7.2 -> qemu-8.0 -M pc-7.2 > +- $ qemu-8.0 -M pc-7.2 -> qemu-7.2 -M pc-7.2 > + > +This two are the ones that work. The whole point of making the > +change in qemu-8.0.1 release was to fix this issue: > + > +- $ qemu-7.2 -M pc-7.2 -> qemu-8.0.1 -M pc-7.2 > +- $ qemu-8.0.1 -M pc-7.2 -> qemu-7.2 -M pc-7.2 > + > +But now we found that qemu-8.0 neither can migrate to qemu-7.2 not > +qemu-8.0.1. > + > +- $ qemu-8.0 -M pc-7.2 -> qemu-8.0.1 -M pc-7.2 > +- $ qemu-8.0.1 -M pc-7.2 -> qemu-8.0 -M pc-7.2 > + > +So, if we start a pc-7.2 machine in qemu-8.0 we can't migrate it to > +anything except to qemu-8.0. > + > +Can we do better? > + > +Yeap. If we know that we are gonig to do this migration: going > + > +- $ qemu-8.0 -M pc-7.2 -> qemu-8.0.1 -M pc-7.2 > + > +We can launche the appropiate devices with "launch" was already pointed out by Peter, but there's also "appropriate" > + > +--device...,x-pci-e-err-unc-mask=on > + > +And now we can receive a migration from 8.0. And from now on, we can > +do that migration to new machine types if we remember to enable that > +property for pc-7.2. Notice that we need to remember, it is not > +enough to know that the source of the migration is qemu-8.0. Think of this > example: > + > +$ qemu-8.0 -M pc-7.2 -> qemu-8.0.1 -M pc-7.2 -> qemu-8.2 -M pc-7.2 > + > +In the second migration, the source is not qemu-8.0, but we still have > +that "problem" and have that property enabled. Notice that we need to > +continue having this mark/property until we have this machine > +rebooted. But it is not a normal reboot (that don't reload qemu) we > +need the mapchine to poweroff/poweron on a fixed qemu. And from now machine Best Regards, Fiona