Last Branch Recording (LBR) is a performance monitor unit (PMU) feature
on Intel CPUs that captures branch related info. This patch series enables
this feature to KVM guests.
Here is a conclusion of the fundamental methods that we use:
1) the LBR feature is enabled per guest via QEMU setting of
KVM_CAP_X86_GUEST_LBR;
2) the LBR stack is passed through to the guest for direct accesses after
the guest's first access to any of the lbr related MSRs;
3) When the guest uses the LBR feature with the user callstack mode, the
host will help save/resotre the LBR stack when the vCPU is scheduled
out/in.
ChangeLog:
v2->v3:
- replaces the pv approach with a lazy save approach to saving the lbr
stack on vCPU switching;
- destroy the host side perf event if the guest is torn down;
- remove the unnecessary event->pmu->stop() before calling
perf_event_release_kernel().
v1->v2:
- add the per guest LBR capability, KVM_CAP_X86_GUEST_LBR;
- save/restore the LBR stack conditionally on the vCPU thread context
switching, instead of on VMX transitions;
- expose MSR_IA32_PERF_CAPABILITIES to the guest.
Like Xu (1):
KVM/x86/vPMU: Add APIs to support host save/restore the guest lbr
stack
Wei Wang (4):
perf/x86: add a function to get the lbr stack
KVM/x86: KVM_CAP_X86_GUEST_LBR
KVM/x86: expose MSR_IA32_PERF_CAPABILITIES to the guest
KVM/x86/lbr: lazy save the guest lbr stack
arch/x86/events/intel/lbr.c | 49 ++++++++++++-
arch/x86/events/perf_event.h | 1 +
arch/x86/include/asm/kvm_host.h | 7 ++
arch/x86/include/asm/perf_event.h | 22 ++++++
arch/x86/kvm/cpuid.c | 2 +-
arch/x86/kvm/pmu.h | 8 +++
arch/x86/kvm/pmu_intel.c | 41 +++++++++++
arch/x86/kvm/vmx.c | 144 ++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/x86.c | 10 +++
include/uapi/linux/kvm.h | 1 +
10 files changed, 281 insertions(+), 4 deletions(-)
--
2.7.4
