[Patch v3 0/6] Perf kvm commands bug fix

Dapeng Mi
2025-09-19T02:18:35Z

This patch-set fixes perf kvm commands issues, like missed memory
allocation check/free, out of range memory access and especially the
issue that fails to sample guest with "perf kvm record/top" commands on
Intel platforms.

Since the change "KVM: x86/pmu: Add basic support to enable guest PEBS
via DS"[1] starts, host loses the capability to sample guest with PEBS
since all PEBS related MSRs are switched to guest value after vm-entry,
like IA32_DS_AREA MSR is switched to guest GVA at vm-entry. This leads
to PEBS events can't be used to sample guest by host, otherwise no guest
PEBS records can be really sampled. The patches 5-6/6 fix this issue by
using "cycles" event instead of PEBS event "cycles:P" to sample guest on
Intel platforms.

Changes:
v2 -> v3:
* Correct the fixes tag in patch 5-6/6.
* Add "acked-by" tag from Namhyung.

v1 -> v2:
* Free memory allocated by strdup().
* Check "--pfm-events" in kvm_add_default_arch_event() as well.
* Opportunistically fix the missed memory allocation and free issue in
builtin-kwork.
* Comments refine.

Tests:
* Run command "perf kvm record -a && perf kvm report" and "perf kvm
top" on Intel Sapphire Rapids platform, guest records can be
captured successfully.
* Since no powerpc platforms on hand, doesn't check the patches on
powerpc. Any test on powerpc is appreciated.

Ref:
[1] https://lore.kernel.org/all/20220411101946.20262-1-likexu@tencent.com/

Dapeng Mi (6):
perf tools kvm: Add missed memory allocation check and free
perf tools kwork: Add missed memory allocation check and free
perf tools kvm: Fix the potential out of range memory access issue
perf tools: Add helper x86__is_intel_cpu()
perf tools kvm: Use "cycles" to sample guest for "kvm record" on Intel
perf tools kvm: Use "cycles" to sample guest for "kvm top" on Intel

tools/perf/arch/x86/util/kvm-stat.c | 51 +++++++++++
tools/perf/builtin-kvm.c | 130 ++++++++++++++++++++--------
tools/perf/builtin-kwork.c | 27 ++++--
tools/perf/util/env.c | 22 +++++
tools/perf/util/env.h | 2 +
tools/perf/util/kvm-stat.h | 10 +++
6 files changed, 203 insertions(+), 39 deletions(-)

base-commit: 576bd7a8c90c48e9e93a18de0bcc0fa1e0a5433b
--
2.34.1