SRU prepared (template in bug description) and tested against the PPA (https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/4389) and reviewed (https://code.launchpad.net/~paelzer/ubuntu/+source/qemu/+git/qemu/+merge/395786 + https://code.launchpad.net/~paelzer/ubuntu/+source/qemu/+git/qemu/+merge/395787).
I will upload that to -unapproved soon ** Description changed: + [Impact] + + Symptom: PCI devices are unavailable after a subsystem reset + Problem: When a subsystem reset event occurs (e.g. via kexec) PCI + devices are not being reset and are therefore in an + unexpected state when the guest attempts to enable them + again after the subsystem reset. This results in the + + [Test Case] + + # Prep a guest and wait until it booted + $ apt install uvtool-libvirt + $ uvt-simplestreams-libvirt --verbose sync --source http://cloud-images.ubuntu.com/daily "arch=s390x" label=daily "release=focal" + $ uvt-kvm create --disk 5 --password=ubuntu testguest release=focal arch=s390x label=daily + $ virsh console testguest + # lspci in guest shows nothing yet (expected) + + # Add virtio device + $ cat > virtio-pci.xml << EOF + <interface type='network'> + <source network='default'/> + <model type='virtio'/> + <address type='pci'/> + <rom bar='off' file=''/> + </interface> + EOF + $ virsh attach-device testguest virtio-pci.xml + + + # lspci in guest now shows the device + ubuntu@testguest:~$ lspci + 0001:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device + + # verify that a "normal" reboot does not loose the device + ubuntu@testguest:~$ sudo reboot + ... + ubuntu@testguest:~$ lspci + 0001:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device + + # Kexec into a kernel (can be the same) + ubuntu@testguest:~$ sudo apt install kexec-tools + ubuntu@testguest:~$ sudo kexec --load /boot/vmlinuz --initrd=/boot/initrd.img --append="$(cat /proc/cmdline)" + ubuntu@testguest:~$ sudo kexec --exec + + # Log in and recheck lspci - it will be empty (wrong) + # With the Fix that will show the pci device again + ubuntu@testguest:~$ lspci + + # Note: A Reboot will get the device back (in old and new case) + + [Where problems could occur] + + * The patch is gladly small - it affects the list of devices that will + be reset them. By extending this list obivously more devices will be + reset - therefore the activity of a "subsystem_reset" will cover more + devices. + Regressions (let us hope not) would happen there. For example think + there is a buggy PCI device that no one cared about before. Formerly it + would not have been reset, but now it is. If that reset fails badly you + have a regression. + Fortunately PCI devices are still uncommon on s390x, so even if (I + doubt) there is a regression it would affect a small fraqction of users + only. + These kind of resets happen on load (kexec, reboot, start) and that is + the place to look out for regressions. + + [Other Info] + + * n/a + + --- + + Description: s390x/s390-virtio-ccw: Reset PCI devices during subsystem reset Symptom: PCI devices are unavailable after a subsystem reset Problem: When a subsystem reset event occurs (e.g. via kexec) PCI - devices are not being reset and are therefore in an - unexpected state when the guest attempts to enable them - again after the subsystem reset. This results in the devices - being unavailable to the guest until a reboot. + devices are not being reset and are therefore in an + unexpected state when the guest attempts to enable them + again after the subsystem reset. This results in the devices + being unavailable to the guest until a reboot. Solution: Add the s390 PCI host bridge to the list of devices to be - reset during a subsystem reset event + reset during a subsystem reset event Reproduction: kexec on an s390x guest with PCI devices db08244a3a7e s390x/s390-virtio-ccw: Reset PCI devices during subsystem reset This fix need to be applied to qemu for focal (20.04) and groovy (20.10). -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1907656 Title: [UBUNTU 21.04] s390x/s390-virtio-ccw: Reset PCI devices during subsystem reset To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1907656/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
