[PATCH v3 0/5] Add support for the Idle HLT intercept feature

Manali Shukla
2024-05-28T04:19:42Z

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.

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].

[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

Testing Done:
- Added a selftest to test the Idle HLT intercept functionality.
- Compile and functionality testing for the Idle HLT intercept selftest
are only done for x86_64.
- Tested SEV and SEV-ES guest for the Idle HLT intercept functionality.

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.

Manali Shukla (5):
x86/cpufeatures: Add CPUID feature bit for Idle HLT intercept
KVM: SVM: Add Idle HLT intercept support
KVM: selftests: Add safe_halt() and cli() helpers to common code
KVM: selftests: Add an interface to read the data of named vcpu stat
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/svm/svm.c | 11 ++-
tools/testing/selftests/kvm/Makefile | 1 +
.../testing/selftests/kvm/include/kvm_util.h | 44 +++++++++
.../kvm/include/x86_64/kvm_util_arch.h | 40 +++++++++
.../selftests/kvm/include/x86_64/processor.h | 18 ++++
tools/testing/selftests/kvm/lib/kvm_util.c | 32 +++++++
.../selftests/kvm/x86_64/svm_idle_hlt_test.c | 89 +++++++++++++++++++
10 files changed, 236 insertions(+), 3 deletions(-)
create mode 100644 tools/testing/selftests/kvm/x86_64/svm_idle_hlt_test.c

base-commit: d91a9cc16417b8247213a0144a1f0fd61dc855dd
--
2.34.1