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:
v3->v4:
- perf/x86:
- Patch 1: change the lbr msr variable type to "unsigned int";
- Patch 6: add a "no_counter" boolean attr to let callers
explicitly tell the perf core to not allocate counters for the
event;
- Patch 7: change "cpuc->vcpu_lbr" from "boolean" to "u8", and add
the PF_VCPU and is_kernel_event checks befoer setting it;
- Patch 8: add the LBR_SELECT save/restore on vCPU switching;
- Patch 9: move lbr_select_user_callstack to .h, instead of
exporting it;
- KVM/x86:
- Patch 3: use "cap->args[0]" to enable/disable the lbr feature
from userspace;
- Patch 4: forbid the enabling the guest lbr when the host and
guest see different lbr stack entries;
- Patch 10: in guest_access_lbr_msr, pass through the lbr stack
only when it has been passed through (i.e. add the check
!vcpu->arch.lbr_used).
previous:
https://lkml.org/lkml/2018/9/20/507
Like Xu (1):
KVM/x86/vPMU: Add APIs to support host save/restore the guest lbr
stack
Wei Wang (9):
perf/x86: fix the variable type of the LBR MSRs
perf/x86: add a function to get the lbr stack
KVM/x86: KVM_CAP_X86_GUEST_LBR
KVM/x86: intel_pmu_lbr_enable
KVM/x86: expose MSR_IA32_PERF_CAPABILITIES to the guest
perf/x86: no counter allocation support
perf/x86: save/restore LBR_SELECT on vCPU switching
perf/x86: function to check lbr user callstack mode
KVM/x86/lbr: lazy save the guest lbr stack
arch/x86/events/core.c | 12 +++
arch/x86/events/intel/lbr.c | 82 ++++++++---------
arch/x86/events/perf_event.h | 6 +-
arch/x86/include/asm/kvm_host.h | 7 ++
arch/x86/include/asm/perf_event.h | 64 +++++++++++++
arch/x86/kvm/cpuid.c | 2 +-
arch/x86/kvm/cpuid.h | 8 ++
arch/x86/kvm/pmu.c | 8 ++
arch/x86/kvm/pmu.h | 10 +++
arch/x86/kvm/pmu_intel.c | 183 ++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/vmx.c | 147 ++++++++++++++++++++++++++++++
arch/x86/kvm/x86.c | 14 +++
include/linux/perf_event.h | 12 +++
include/uapi/linux/kvm.h | 1 +
include/uapi/linux/perf_event.h | 3 +-
kernel/events/core.c | 7 --
16 files changed, 514 insertions(+), 52 deletions(-)
--
2.7.4
