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authorChristian Krinitsin <mail@krinitsin.com>2025-06-16 16:59:00 +0000
committerChristian Krinitsin <mail@krinitsin.com>2025-06-16 16:59:33 +0000
commit9aba81d8eb048db908c94a3c40c25a5fde0caee6 (patch)
treeb765e7fb5e9a3c2143c68b0414e0055adb70e785 /results/classifier/118/kernel/1745895
parentb89a938452613061c0f1f23e710281cf5c83cb29 (diff)
downloadqemu-analysis-9aba81d8eb048db908c94a3c40c25a5fde0caee6.tar.gz
qemu-analysis-9aba81d8eb048db908c94a3c40c25a5fde0caee6.zip
add 18th iteration of classifier
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+kernel: 0.958
+device: 0.949
+ppc: 0.908
+PID: 0.906
+user-level: 0.901
+debug: 0.894
+network: 0.878
+socket: 0.877
+architecture: 0.877
+virtual: 0.872
+hypervisor: 0.857
+peripherals: 0.833
+performance: 0.830
+graphic: 0.803
+mistranslation: 0.793
+semantic: 0.763
+register: 0.745
+permissions: 0.734
+VMM: 0.719
+risc-v: 0.698
+vnc: 0.687
+TCG: 0.684
+x86: 0.661
+boot: 0.652
+arm: 0.605
+KVM: 0.602
+assembly: 0.587
+files: 0.556
+i386: 0.520
+
+Unable to migrate vhost-net to virtio-1.0-capable kernel
+
+I am running QEMU 2.11 (from upstream source, not Red Hat package) on stock RHEL 6 and RHEL 7 kernels. Only the RHEL 7 kernel supports VIRTIO_F_VERSION_1 in its vhost-net driver.
+
+When migrating a guest using vhost-net from the RHEL 6 host to RHEL 7, the PCI config is rejected by QEMU on the target machine.
+
+A simple test case:
+
+1. On the RHEL 7 host, prepare for an incoming migration:
+
+  rhel7# qemu-system-x86_64 -S -accel kvm -nographic -monitor stdio -nodefaults -netdev tap,id=net0,vhost=on,script=no,downscript=no -device virtio-net-pci,netdev=net0,mac=54:52:00:ff:ff:ff -incoming tcp:0.0.0.0:12345
+
+2. On the RHEL 6 host, start a guest and migrate it to the RHEL 7 host:
+
+  rhel6# qemu-system-x86_64 -S -accel kvm -nographic -monitor stdio -nodefaults -netdev tap,id=net0,vhost=on,script=no,downscript=no -device virtio-net-pci,netdev=net0,mac=54:52:00:ff:ff:ff
+QEMU 2.11.0 monitor - type 'help' for more information
+  (qemu) migrate tcp:rhel7:12345
+
+The RHEL 7 QEMU errors out:
+
+  qemu-system-x86_64: get_pci_config_device: Bad config data: i=0x20 read: 0 device: c cmask: ff wmask: 0 w1cmask:0
+  qemu-system-x86_64: Failed to load PCIDevice:config
+  qemu-system-x86_64: Failed to load virtio-net:virtio
+  qemu-system-x86_64: error while loading state for instance 0x0 of device '0000:00:02.0/virtio-net'
+  qemu-system-x86_64: load of migration failed: Invalid argument
+
+If I start the source QEMU with vhost=off, or the target QEMU with disable-modern=true, the migration is successful.
+
+My hunch here is that the target QEMU prepares the PCI device to support VIRTIO_F_VERSION_1, as that's available in the kernel there, but then fails to (or does not know to) disable this during the migration.
+
+The QEMU project is currently considering to move its bug tracking to another system. For this we need to know which bugs are still valid and which could be closed already. Thus we are setting older bugs to "Incomplete" now.
+If you still think this bug report here is valid, then please switch the state back to "New" within the next 60 days, otherwise this report will be marked as "Expired". Or mark it as "Fix Released" if the problem has been solved with a newer version of QEMU already. Thank you and sorry for the inconvenience.
+
+[Expired for QEMU because there has been no activity for 60 days.]
+