Package: release.debian.org Severity: normal Tags: buster User: release.debian....@packages.debian.org Usertags: pu X-Debbugs-Cc: no...@debian.org
There are two parts to the proposed changes: 1. Support in arm64 KVM code for reporting stolen time to guests. 2. Support in arm64 paravirtualised guest code for requesting stolen time from the hypervisor and reporting it to user-space. I think part 1 is not suitable for a stable update, but part 2 might be. [ Reason ] Noah Meyerhans wrote in bug #969443: > When used in virtual machine environments, Linux on amd64 is able to report > "steal time" to the guest. This functionality has been supported by Linux > on amd64 for years, but was only added to arm64 with Linux 5.5. > > As Debian and arm64 are increasingly used in virtual environments, including > cloud environments, the ability to report steal time is increasingly > important for system monitoring and performance analysis. Thus, I'd like to > request that CPU steal time accounting support for arm64 be backported to > buster, if possible. [ Impact ] Without this, it's difficult to determine when VM performance is being affected by stolen time. [ Tests ] Noah has tested the changes (at least part 2) in an arm64 KVM environment with steal time reporting, presumably AWS EC2. [ Risks ] There is a potential to regress VM host and/or guest support on arm64 and armhf, depending on which part(s) are applied. [ Changes ] 1. * KVM: arm64: Document PV-time interface * KVM: arm/arm64: Factor out hypercall handling from PSCI * KVM: arm64: Implement PV_TIME_FEATURES call * KVM: Implement kvm_put_guest() * KVM: arm64: Support stolen time reporting via shared * KVM: Allow kvm_device_ops to be const * KVM: arm64: Provide VCPU attributes for stolen time 2. * arm/arm64: smccc/psci: add arm_smccc_1_1_get_conduit() * arm/arm64: Provide a wrapper for SMCCC 1.1 calls * arm/arm64: Make use of the SMCCC 1.1 wrapper * arm64: Retrieve stolen time as paravirtualized guest The actual patches are visible at <https://salsa.debian.org/kernel-team/linux/-/merge_requests/268>. Ben. -- System Information: Debian Release: bullseye/sid APT prefers unstable-debug APT policy: (500, 'unstable-debug'), (500, 'stable-updates'), (500, 'unstable'), (500, 'stable'), (1, 'experimental') Architecture: amd64 (x86_64) Foreign Architectures: i386 Kernel: Linux 5.9.0-2-amd64 (SMP w/2 CPU threads) Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE not set Shell: /bin/sh linked to /bin/dash Init: systemd (via /run/systemd/system) LSM: AppArmor: enabled
