This series makes it so that the time that the host is suspended is included in guests' steal time. When the host resumes from a suspend, the guest thinks any task that was running during the suspend ran for a long time, even though the effective run time was much shorter, which can end up having negative effects with scheduling. To mitigate this issue, include the time that the host was suspended in steal time, if the guest requests it, which lets the guest subtract the duration from the tasks' runtime. Add new ABI to make this behavior opt-in per-guest. In addition, make the guest TSC behavior consistent whether the host TSC went backwards or not. v7: - Fix build. - Make advancing TSC dependent on X86_64. v6: https://lore.kernel.org/kvm/20250709070450.473297-1-suleiman@xxxxxxxxxx/ - Use true/false for bools. - Indentation. - Remove superfluous flag. - Use atomic operations for accumulating suspend duration. - Reuse generic vcpu block/kick infrastructure instead of rolling our own. - Add ABI to make the behavior opt-in per-guest. - Add command line parameter to make guest use this. - Reword commit messages in imperative mood. v5: https://lore.kernel.org/kvm/20250325041350.1728373-1-suleiman@xxxxxxxxxx/ - Fix grammar mistakes in commit message. v4: https://lore.kernel.org/kvm/20250221053927.486476-1-suleiman@xxxxxxxxxx/ - Advance guest TSC on suspends where host TSC goes backwards. - Block vCPUs from running until resume notifier. - Move suspend duration accounting out of machine-independent kvm to x86. - Merge code and documentation patches. - Reworded documentation. v3: https://lore.kernel.org/kvm/20250107042202.2554063-1-suleiman@xxxxxxxxxx/ - Use PM notifier instead of syscore ops (kvm_suspend()/kvm_resume()), because the latter doesn't get called on shallow suspend. - Don't call function under UACCESS. - Whitespace. v2: https://lore.kernel.org/kvm/20240820043543.837914-1-suleiman@xxxxxxxxxx/ - Accumulate suspend time at machine-independent kvm layer and track per-VCPU instead of per-VM. - Document changes. v1: https://lore.kernel.org/kvm/20240710074410.770409-1-suleiman@xxxxxxxxxx/ Suleiman Souhlal (3): KVM: x86: Advance guest TSC after deep suspend. KVM: x86: Include host suspended duration in steal time KVM: x86: Add "suspendsteal" cmdline to request host to add suspend duration in steal time .../admin-guide/kernel-parameters.txt | 5 + Documentation/virt/kvm/x86/cpuid.rst | 4 + Documentation/virt/kvm/x86/msr.rst | 14 +++ arch/x86/include/asm/kvm_host.h | 6 + arch/x86/include/uapi/asm/kvm_para.h | 2 + arch/x86/kernel/kvm.c | 15 +++ arch/x86/kvm/cpuid.c | 4 +- arch/x86/kvm/x86.c | 112 +++++++++++++++++- 8 files changed, 156 insertions(+), 6 deletions(-) -- 2.50.0.727.gbf7dc18ff4-goog
