I recently noticed that some developers particularly like the PT feature.
So please help review this version since a new kernel cycle has begun .
Intel new hardware (Atom processors based on the Tremont microarchitecture)
introduces some Processor Event-Based Sampling (PEBS) extensions that output
the PEBS record to Intel PT stream instead of DS area. The PEBS record will
be packaged in a specific format when outputting to Intel PT buffer.
To use PEBS-via-PT, the guest driver will firstly check the basic support
for PEBS-via-DS, so this patch set is based on the PEBS-via-DS enabling
patch set [1].
We can use PEBS-via-PT feature on the Linux guest like native:
(you may need modprobe kvm-intel.ko with pt_mode=1)
Recording is selected by using the aux-output config term e.g.
$ perf record -c 10000 -e '{intel_pt/branch=0/,cycles/aux-output/ppp}' uname
Warning:
Intel Processor Trace: TSC not available
Linux
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.028 MB perf.data ]
To display PEBS events from the Intel PT trace, use the itrace 'o' option e.g.
$ perf script --itrace=oe
uname 853 113.230292: 10000 cycles/aux-output/ppp: ffffffff8125dcd9 perf_output_begin+0x29 ([kernel.kallsyms])
uname 853 113.230443: 10000 cycles/aux-output/ppp: ffffffff8106de86 native_write_msr+0x6 ([kernel.kallsyms])
uname 853 113.230444: 10000 cycles/aux-output/ppp: ffffffff81bd035b exc_nmi+0x10b ([kernel.kallsyms])
uname 853 113.230567: 10000 cycles/aux-output/ppp: ffffffff8106de86 native_write_msr+0x6 ([kernel.kallsyms])
uname 853 113.230567: 10000 cycles/aux-output/ppp: ffffffff8125dce0 perf_output_begin+0x30 ([kernel.kallsyms])
uname 853 113.230688: 10000 cycles/aux-output/ppp: ffffffff8106de86 native_write_msr+0x6 ([kernel.kallsyms])
uname 853 113.230689: 10000 cycles/aux-output/ppp: ffffffff81005da7 perf_event_nmi_handler+0x7 ([kernel.kallsyms])
uname 853 113.230816: 10000 cycles/aux-output/ppp: ffffffff8106de86 native_write_msr+0x6 ([kernel.kallsyms])
Please check more details in each commit and feel free to comment.
V2 -> V3 Changelog:
- Add x86_pmu.pebs_vmx to ATOM_TREMONT and support PDIR counter;
- Rewrite get_gp_pmc() and get_fixed_pmc() based on PERF_CAP_PEBS_OUTPUT_PT;
- Check and add counter reload registers in the intel_guest_get_msrs();
- Expose this capability in the vmx_get_perf_capabilities();
Previous:
https://lore.kernel.org/kvm/1584628430-23220-1-git-send-email-luwei.kang@xxxxxxxxx/
[1] https://lore.kernel.org/kvm/20210511024214.280733-1-like.xu@xxxxxxxxxxxxxxx/
Like Xu (4):
KVM: x86/pmu: Add pebs_vmx support for ATOM_TREMONT
KVM: x86/pmu: Add counter reload MSR emulation for all counters
KVM: x86/pmu: Add counter reload registers to the MSR-load list
KVM: x86/pmu: Expose PEBS-via-PT in the KVM supported capabilities
Luwei Kang (1):
KVM: x86/pmu: Add the base address parameter for get_fixed_pmc()
arch/x86/events/intel/core.c | 28 +++++++++++++++++++++++++
arch/x86/events/perf_event.h | 5 -----
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/include/asm/msr-index.h | 6 ++++++
arch/x86/kvm/pmu.c | 5 ++---
arch/x86/kvm/pmu.h | 11 ++++++++--
arch/x86/kvm/vmx/capabilities.h | 5 ++++-
arch/x86/kvm/vmx/pmu_intel.c | 35 ++++++++++++++++++++++++++------
arch/x86/kvm/vmx/vmx.h | 2 +-
9 files changed, 80 insertions(+), 18 deletions(-)
--
2.31.1
