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Message-ID: <c4798418-9530-bc4c-2218-313d3e99bfa0@amd.com>
Date: Tue, 16 Aug 2022 10:40:19 +0530
From: Sandipan Das <sandipan.das@....com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Olsa <olsajiri@...il.com>, linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org, x86@...nel.org,
peterz@...radead.org, bp@...en8.de, namhyung@...nel.org,
tglx@...utronix.de, mingo@...hat.com, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, dave.hansen@...ux.intel.com,
like.xu.linux@...il.com, eranian@...gle.com,
ananth.narayan@....com, ravi.bangoria@....com,
santosh.shukla@....com
Subject: Re: [PATCH 2/4] tools headers x86: Sync msr-index.h with kernel
sources
Hi Arnaldo,
On 8/13/2022 1:09 AM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Aug 12, 2022 at 02:33:46PM +0530, Sandipan Das escreveu:
>> Hi Jiri,
>>
>> On 8/12/2022 2:03 PM, Jiri Olsa wrote:
>>> On Thu, Aug 11, 2022 at 06:16:47PM +0530, Sandipan Das wrote:
>>>> Sync msr-index.h with the kernel sources by adding the new AMD Last Branch
>>>> Record Extension Version 2 (LbrExtV2) MSRs.
>>>>
>>>> Signed-off-by: Sandipan Das <sandipan.das@....com>
>>>> ---
>>>> tools/arch/x86/include/asm/msr-index.h | 5 +++++
>>>> 1 file changed, 5 insertions(+)
>>>>
>>>> diff --git a/tools/arch/x86/include/asm/msr-index.h b/tools/arch/x86/include/asm/msr-index.h
>>>> index cc615be27a54..7f9eaf497947 100644
>>>> --- a/tools/arch/x86/include/asm/msr-index.h
>>>> +++ b/tools/arch/x86/include/asm/msr-index.h
>>>> @@ -574,6 +574,9 @@
>>>> #define MSR_AMD64_PERF_CNTR_GLOBAL_CTL 0xc0000301
>>>> #define MSR_AMD64_PERF_CNTR_GLOBAL_STATUS_CLR 0xc0000302
>>>>
>>>> +/* AMD Last Branch Record MSRs */
>>>> +#define MSR_AMD64_LBR_SELECT 0xc000010e
>>>
>>> curious do we actualy use this in tools somewhere?
>>>
>>> jirka
>>>
>>
>> Commit 9dde6cadb92b ("tools arch x86: Sync the msr-index.h copy with the kernel sources")
>> from Arnaldo says that adding these new MSR definitions in the tools headers allows the
>> beautification scripts to pick up new entries which can be used for filtering MSR access
>> traces.
>>
>> E.g. one can trace the hardware LBR branch filter bits getting written to the LBR_SELECT
>> MSR while recording branches.
>>
>> $ perf record -j any,u true
>> $ perf record -j any_call,u true
>>
>> $ sudo perf trace -e msr:write_msr/max-stack=32/ --filter="msr == AMD64_LBR_SELECT"
>>
>> [...]
>> 224568.130 perf/9093 msr:write_msr(msr: AMD64_LBR_SELECT, val: 1)
>> do_trace_write_msr ([kernel.kallsyms])
>> do_trace_write_msr ([kernel.kallsyms])
>> native_write_msr ([kernel.kallsyms])
>> amd_pmu_lbr_enable_all ([kernel.kallsyms])
>> amd_pmu_v2_enable_all ([kernel.kallsyms])
>> x86_pmu_enable ([kernel.kallsyms])
>> ctx_resched ([kernel.kallsyms])
>> perf_event_exec ([kernel.kallsyms])
>> begin_new_exec ([kernel.kallsyms])
>> load_elf_binary ([kernel.kallsyms])
>> bprm_execve ([kernel.kallsyms])
>> do_execveat_common.isra.0 ([kernel.kallsyms])
>> __x64_sys_execve ([kernel.kallsyms])
>> do_syscall_64 ([kernel.kallsyms])
>> entry_SYSCALL_64 ([kernel.kallsyms])
>> execve (/usr/lib/x86_64-linux-gnu/libc.so.6)
>> [...]
>> 302748.439 perf/9126 msr:write_msr(msr: AMD64_LBR_SELECT, val: 229)
>> do_trace_write_msr ([kernel.kallsyms])
>> do_trace_write_msr ([kernel.kallsyms])
>> native_write_msr ([kernel.kallsyms])
>> amd_pmu_lbr_enable_all ([kernel.kallsyms])
>> amd_pmu_v2_enable_all ([kernel.kallsyms])
>> x86_pmu_enable ([kernel.kallsyms])
>> ctx_resched ([kernel.kallsyms])
>> perf_event_exec ([kernel.kallsyms])
>> begin_new_exec ([kernel.kallsyms])
>> load_elf_binary ([kernel.kallsyms])
>> bprm_execve ([kernel.kallsyms])
>> do_execveat_common.isra.0 ([kernel.kallsyms])
>> __x64_sys_execve ([kernel.kallsyms])
>> do_syscall_64 ([kernel.kallsyms])
>> entry_SYSCALL_64 ([kernel.kallsyms])
>> execve (/usr/lib/x86_64-linux-gnu/libc.so.6)
>> [...]
>>
>> I can add this example to the commit message in the next revision.
>
> Right, you can reuse something from my messages updating this file or,
> better, show an example like you did above, for the thing that you are
> working at that moment :-)
>
> One of the things we need to do is:
>
> perf trace -e msr:write_msr/max-stack=32/ --filter-help
>
> And then it should look what are the strings that can be used for that
> specific msr:write_msr tracepoint.
>
> Also have tab expansion in the --filter= part :-)
>
Thanks for the suggestions. Will incorporate them in the next revision.
- Sandipan
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