Re: [PATCH V2 2/6] perf: Add branch stack extension

[Sandipan Das]

Hi Kan,

On 5/22/2023 5:00 PM, kan.liang@xxxxxxxxxxxxxxx wrote:
> From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> 
> Currently, the extra information of a branch entry is stored in a u64
> space. With more and more information added, the space is running out.
> For example, the information of occurrences of events will be added for
> each branch.
> 
> Add an extension space to record the new information for each branch
> entry. The space is appended after the struct perf_branch_stack.
> 
> Add a bit in struct perf_branch_entry to indicate whether the extra
> information is included.
> 
> Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> Cc: Sandipan Das <sandipan.das@xxxxxxx>
> Cc: Ravi Bangoria <ravi.bangoria@xxxxxxx>
> Cc: Athira Rajeev <atrajeev@xxxxxxxxxxxxxxxxxx>
> ---
> 
> New patch
> - Introduce a generic extension space which can be used to
>   store the LBR event information for Intel. It can also be used by
>   other ARCHs for the other purpose.
> - Add a new bit in struct perf_branch_entry to indicate whether the
>   extra information is included.
> 
>  arch/powerpc/perf/core-book3s.c |  2 +-
>  arch/x86/events/amd/core.c      |  2 +-
>  arch/x86/events/intel/core.c    |  2 +-
>  arch/x86/events/intel/ds.c      |  4 ++--
>  include/linux/perf_event.h      | 18 +++++++++++++++++-
>  include/uapi/linux/perf_event.h |  4 +++-
>  kernel/events/core.c            |  5 +++++
>  7 files changed, 30 insertions(+), 7 deletions(-)
> 

This seems to be missing the following:

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 6310fc5c9f52..b6739f63dc34 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1704,7 +1704,7 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
                perf_sample_data_init(&data, 0, event->hw.last_period);

                if (has_branch_stack(event))
-                       perf_sample_save_brstack(&data, event, &cpuc->lbr_stack);
+                       perf_sample_save_brstack(&data, event, &cpuc->lbr_stack, NULL);

                if (perf_event_overflow(event, &data, regs))
                        x86_pmu_stop(event, 0);


Otherwise, the changes look good to me.

Reviewed-by: Sandipan Das <sandipan.das@xxxxxxx>