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) when the guest has the LBR feature, the LBR stack is passed through to
the guest for direct accesses;
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 thread is
scheduled out/in.
Patches 1-5 implements the above 1) and 2), and patches 6-8 implements
the above 3).
ChangeLog:
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.
The first version was sent out long time ago, and can be referenced here:
https://lkml.org/lkml/2017/9/25/11 , and thanks for lots of the
suggestions from Paolo Bonzini and Andi Kleen.
Like Xu (2):
KVM: PMU: support to save/restore the guest lbr stack on vCPU
switching
perf/x86/intel/lbr: add the guest_lbr boolean to cpuc
Wei Wang (6):
perf/x86: add a function to get the lbr stack
KVM/x86: KVM_CAP_X86_GUEST_LBR
KVM/vmx: Pass through the lbr stack to a guest
KVM/x86: expose MSR_IA32_PERF_CAPABILITIES to the guest
KVM/x86: enable the guest to access the debugctl msr
perf/x86/intel/lbr: guest requesting KVM for lbr stack save/restore
arch/x86/events/intel/lbr.c | 54 +++++++++++++++++++++++++--
arch/x86/events/perf_event.h | 1 +
arch/x86/include/asm/kvm_host.h | 3 ++
arch/x86/include/asm/perf_event.h | 19 ++++++++++
arch/x86/include/uapi/asm/kvm_para.h | 2 +
arch/x86/kvm/cpuid.c | 5 ++-
arch/x86/kvm/pmu_intel.c | 71 +++++++++++++++++++++++++++++++++++-
arch/x86/kvm/vmx.c | 60 ++++++++++++++++++++++++++++++
arch/x86/kvm/x86.c | 18 +++------
include/uapi/linux/kvm.h | 1 +
10 files changed, 215 insertions(+), 19 deletions(-)
--
2.7.4
