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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <28bf94c1-3b8f-4036-9aa2-b64b9f6edb0c@linux.intel.com>
Date: Wed, 3 Sep 2025 14:32:18 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...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>, Kevin Tian <kevin.tian@...el.com>,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [Patch v2 0/6] Perf kvm commands bug fix


On 8/16/2025 4:15 AM, Namhyung Kim wrote:
> On Mon, Aug 11, 2025 at 01:55:40PM +0800, Dapeng Mi wrote:
>> 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
> Acked-by: Namhyung Kim <namhyung@...nel.org>

Namhyung, thanks for your ack. Do you think is it good to be queued or
still need other acks? 


>
> Thanks,
> Namhyung
>
>>  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
>>