On 10/22/2024 11:18 AM, Manali Shukla wrote: > The upcoming new Idle HLT Intercept feature allows for the HLT > instruction execution by a vCPU to be intercepted by the hypervisor > only if there are no pending V_INTR and V_NMI events for the vCPU. > When the vCPU is expected to service the pending V_INTR and V_NMI > events, the Idle HLT intercept won’t trigger. The feature allows the > hypervisor to determine if the vCPU is actually idle and reduces > wasteful VMEXITs. > > The idle HLT intercept feature is used for enlightened guests who wish > to securely handle the events. When an enlightened guest does a HLT > while an interrupt is pending, hypervisor will not have a way to > figure out whether the guest needs to be re-entered or not. The Idle > HLT intercept feature allows the HLT execution only if there are no > pending V_INTR and V_NMI events. > > Presence of the Idle HLT Intercept feature is indicated via CPUID > function Fn8000_000A_EDX[30]. > > Document for the Idle HLT intercept feature is available at [1]. > > This series is based on kvm-next/next (64dbb3a771a1) + [2]. > > Experiments done: > ---------------- > > kvm_amd.avic is set to '0' for this experiment. > > The below numbers represent the average of 10 runs. > > Normal guest (L1) > The below netperf command was run on the guest with smp = 1 (pinned). > > netperf -H <host ip> -t TCP_RR -l 60 > ---------------------------------------------------------------- > |with Idle HLT(transactions/Sec)|w/o Idle HLT(transactions/Sec)| > ---------------------------------------------------------------- > | 25645.7136 | 25773.2796 | > ---------------------------------------------------------------- > > Number of transactions/sec with and without idle HLT intercept feature > are almost same. > > Nested guest (L2) > The below netperf command was run on L2 guest with smp = 1 (pinned). > > netperf -H <host ip> -t TCP_RR -l 60 > ---------------------------------------------------------------- > |with Idle HLT(transactions/Sec)|w/o Idle HLT(transactions/Sec)| > ---------------------------------------------------------------- > | 5655.4468 | 5755.2189 | > ---------------------------------------------------------------- > > Number of transactions/sec with and without idle HLT intercept feature > are almost same. > > Testing Done: > - Tested the functionality for the Idle HLT intercept feature > using selftest svm_idle_hlt_test. > - Tested SEV and SEV-ES guest for the Idle HLT intercept functionality. > - Tested the Idle HLT intercept functionality on nested guest. > > v3 -> v4 > - Drop the patches to add vcpu_get_stat() into a new series [2]. > - Added nested Idle HLT intercept support. > > v2 -> v3 > - Incorporated Andrew's suggestion to structure vcpu_stat_types in > a way that each architecture can share the generic types and also > provide its own. > > v1 -> v2 > - Done changes in svm_idle_hlt_test based on the review comments from Sean. > - Added an enum based approach to get binary stats in vcpu_get_stat() which > doesn't use string to get stat data based on the comments from Sean. > - Added self_halt() and cli() helpers based on the comments from Sean. > > [1]: AMD64 Architecture Programmer's Manual Pub. 24593, April 2024, > Vol 2, 15.9 Instruction Intercepts (Table 15-7: IDLE_HLT). > https://bugzilla.kernel.org/attachment.cgi?id=306250 > > [2]: https://lore.kernel.org/kvm/20241021062226.108657-1-manali.shukla@xxxxxxx/T/#t > > Manali Shukla (4): > x86/cpufeatures: Add CPUID feature bit for Idle HLT intercept > KVM: SVM: Add Idle HLT intercept support > KVM: nSVM: implement the nested idle halt intercept > KVM: selftests: KVM: SVM: Add Idle HLT intercept test > > arch/x86/include/asm/cpufeatures.h | 1 + > arch/x86/include/asm/svm.h | 1 + > arch/x86/include/uapi/asm/svm.h | 2 + > arch/x86/kvm/governed_features.h | 1 + > arch/x86/kvm/svm/nested.c | 7 ++ > arch/x86/kvm/svm/svm.c | 15 +++- > tools/testing/selftests/kvm/Makefile | 1 + > .../selftests/kvm/include/x86_64/processor.h | 1 + > .../selftests/kvm/x86_64/svm_idle_hlt_test.c | 89 +++++++++++++++++++ > 9 files changed, 115 insertions(+), 3 deletions(-) > create mode 100644 tools/testing/selftests/kvm/x86_64/svm_idle_hlt_test.c > > > base-commit: c8d430db8eec7d4fd13a6bea27b7086a54eda6da > prerequisite-patch-id: ca912571db5c004f77b70843b8dd35517ff1267f > prerequisite-patch-id: 164ea3b4346f9e04bc69819278d20f5e1b5df5ed > prerequisite-patch-id: 90d870f426ebc2cec43c0dd89b701ee998385455 > prerequisite-patch-id: 45812b799c517a4521782a1fdbcda881237e1eda A gentle reminder. -Manali
