[PATCH v2 0/8] Guest LBR Enabling

[Wei Wang]

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(-)

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2.7.4