** Tags removed: verification-needed-bionic verification-needed-focal verification-needed-hirsute verification-needed-impish ** Tags added: verification-done-bionic verification-done-focal verification-done-hirsute verification-done-impish
-- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-azure-4.15 in Ubuntu. https://bugs.launchpad.net/bugs/1952234 Title: linux-azure: add Icelake servers support in no-HWP mode to cpufreq/intel_pstate driver Status in linux-azure package in Ubuntu: Fix Released Status in linux-azure-4.15 package in Ubuntu: Invalid Status in linux-azure source package in Bionic: Invalid Status in linux-azure-4.15 source package in Bionic: Fix Committed Status in linux-azure source package in Focal: Fix Committed Status in linux-azure-4.15 source package in Focal: Invalid Status in linux-azure source package in Hirsute: Fix Committed Status in linux-azure-4.15 source package in Hirsute: Invalid Status in linux-azure source package in Impish: Fix Committed Status in linux-azure-4.15 source package in Impish: Invalid Bug description: [SRU Justification] [Impact] Starting with the AH2020 Azure host build, Hyper-V is virtualizing some registers that provide information about the CPU frequency. The registers are read-only in a guest VM, so the guest can see the frequency, but cannot make any modifications. This feature also requires that the VM Configuration Version be 9.2 or later, which means it needs to be a new VM type, such as the just introduced Dv5/Ev5 series, and the new M832v2 VMs. Within the Linux VM, the presence of the feature is indicated by the “aperfmperf” flag in the “lscpu” flags output (or in the flags field in /proc/cpuinfo). It turns out there is a Linux kernel limitation when running on the new Intel IceLake processors used for the Dv5/Ev5 series. Upstream commit fbdc21e9b038 was added to provide IceLake support in the 5.14 kernel. Microsoft has asked to backport fbdc21e9b038 commit to all supported kernels. [Test Plan] Run Intel IceLake based VM and check the "aperfmperf" flag in the "lscpu" flags output. Without the patch the intel_pstate directory is missing from /sys/devices/system/cpu/ and /sys/devices/system/cpu/cpufreq/ is empty. [Where problems could occur] * intel_pstate driver is always used on Intel IceLake based VMs without checking for presence of "aperfmperf" CPU flag. * In earlier (5.4 and 4.15) linux-azure kernels when intel_pstate driver is used it is in "active" mode instead of "passive" one (as reported by "cat /sys/devices/system/cpu/intel_pstate/status", also "cat /sys/devices/system/cpu/cpufreq/policy0/scaling_driver" returns "intel_pstate" instead of "intel_cpufreq" which is the expected behavior when in "active" mode). If a consistent behavior across all kernel versions is desired commit 33aa46f252c7 ("cpufreq: intel_pstate: Use passive mode by default without HWP") from the upstream should probably also be backported. * /sys/devices/system/cpu/cpufreq/policy*/scaling_{min,max}_freq files can be modified and the values reported by kernel will no longer match the values used by hardware. [Other Info] None. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/1952234/+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
