linux-kernel - [Patch v2 0/6] Perf kvm commands bug fix

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Message-Id: <20250811055546.296678-1-dapeng1.mi@linux.intel.com>
Date: Mon, 11 Aug 2025 13:55:40 +0800
From: Dapeng Mi <dapeng1.mi@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Kan Liang <kan.liang@...ux.intel.com>
Cc: Kevin Tian <kevin.tian@...el.com>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Dapeng Mi <dapeng1.mi@...el.com>,
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [Patch v2 0/6] Perf kvm commands bug fix

his 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.

The commit 634d36f82517 ("perf record: Just use "cycles:P" as the
 default event") changes to use PEBS event to do sampling by default
including guest sampling. This breaks host to sample guest with commands
"perf kvm record/top" 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:
  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: 6235ce77749f45cac27f630337e2fdf04e8a6c73
-- 
2.34.1