It looks like a fix for this issue is already in the 137 kernel. The change log for the -136 update shows a single change related to Hyper-V, and that change broke the ability to open /dev/fb0 and mmap it, which is what the graphic desktop will do. Running in non-graphics mode with just a shell and with ‘ssh’ access works fine, which is why Azure VMs didn’t see the issue.
The original change went into the mainline Linux kernel version 5.10, and the change is correct there. It provides a significant performance improvement for the Hyper-V frame buffer. So we wanted it backported to the older releases. Unfortunately, a straight backport breaks in kernel version 5.4 and earlier. The backport needs a minor modification to work correctly 4.15, but we didn’t spot that immediately, mostly because we rarely use graphic desktops. The 4.15.0-137.141 kernel in the queue already, so this issue will be resolved and it only affects 136 - not 135 or 137. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1917958 Title: Latest linux-generic package (kernel 4.15.0-136) doesn't work on HyperV Gen2 VM Status in linux package in Ubuntu: Confirmed Bug description: On Ubuntu 18.04 LTS 1&2 (so far tested), either when deploying a new VM (which pulls the latest linux-generic) or rebooting a VM (which updated the linux-generic under the cover which installs 4.15.0-136) will prevent the VM to boot. After reboot, will get stuck on /dev/sdX: clean, x / y files, k / m blocks. Using grub, selecting an older kernel, allow the VM to book without any issues. I manually installed kernel 4.15.0-135, however the issue doesn't repro. Finally I've verified that this repro on both Server 2016 and Server 2019 versions of Windows... Output of /proc/version_signature (both on Server 2016/2019) Ubuntu 4.15.0-29.31-generic 4.15.18 lspci -vnvn reported empty on this VM. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1917958/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
