Re: [PATCH v2 3/8] perf test ibs: Remove obsolete privilege test

Re: [PATCH v2 3/8] perf test ibs: Remove obsolete privilege test

[Namhyung Kim]

Hello,

On Thu, Apr 30, 2026 at 06:11:10AM +0000, Ravi Bangoria wrote:
> Older IBS implementations lacked a hardware privilege filter, so the
> kernel enabled swfilt=1. Newer AMD CPUs will provide privilege filtering
> via the RIP[63] bit, making swfilt redundant. Remove the perf unit test
> that assumes IBS has no hardware-assisted privilege filter.

Can you add a check for CPU model or capability for this?
Probably we want to keep this test for older models..

Thanks,
Namhyung

> 
> swfilt is ignored by kernel on platforms that support RIP[63] bit filter
> i.e. all amd-ibs-swfilt.sh tests will test hardware assisted privilege
> filter.
> 
> Without the patch:
> 
>   # ./perf test -vv 75
>   test child forked, pid 26029
>   check availability of IBS swfilt
>   run perf record with modifier and swfilt
>   [FAIL] IBS PMU should not accept exclude_kernel
>    75: AMD IBS software filtering                            : FAILED!
> 
> With the patch:
> 
>   # ./perf test -vv 75
>   check availability of IBS swfilt
>   run perf record with modifier and swfilt
>   [ perf record: Woken up 3 times to write data ]
>   [ perf record: Captured and wrote 0.000 MB /dev/null ]
>   [ perf record: Woken up 3 times to write data ]
>   [ perf record: Captured and wrote 0.000 MB /dev/null ]
>   [ perf record: Woken up 3 times to write data ]
>   [ perf record: Captured and wrote 0.000 MB /dev/null ]
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Captured and wrote 0.000 MB /dev/null ]
>   check number of samples with swfilt
>   [ perf record: Woken up 5 times to write data ]
>   [ perf record: Captured and wrote 0.040 MB - ]
>   [ perf record: Woken up 3 times to write data ]
>   [ perf record: Captured and wrote 0.054 MB - ]
>    75: AMD IBS software filtering                            : Ok
> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
> ---
>  tools/perf/tests/shell/amd-ibs-swfilt.sh | 7 -------
>  1 file changed, 7 deletions(-)
> 
> diff --git a/tools/perf/tests/shell/amd-ibs-swfilt.sh b/tools/perf/tests/shell/amd-ibs-swfilt.sh
> index e7f66df05c4b..92ef45bf3043 100755
> --- a/tools/perf/tests/shell/amd-ibs-swfilt.sh
> +++ b/tools/perf/tests/shell/amd-ibs-swfilt.sh
> @@ -22,13 +22,6 @@ fi
>  echo "run perf record with modifier and swfilt"
>  err=0
>  
> -# setting any modifiers should fail
> -perf record -B -e ibs_op//u -o /dev/null true 2> /dev/null
> -if [ $? -eq 0 ]; then
> -    echo "[FAIL] IBS PMU should not accept exclude_kernel"
> -    exit 1
> -fi
> -
>  # setting it with swfilt should be fine
>  perf record -B -e ibs_op/swfilt/u -o /dev/null true
>  if [ $? -ne 0 ]; then
> -- 
> 2.43.0
> 

Re: [PATCH v2 3/8] perf test ibs: Remove obsolete privilege test

[Ravi Bangoria]

>> Older IBS implementations lacked a hardware privilege filter, so the
>> kernel enabled swfilt=1. Newer AMD CPUs will provide privilege filtering
>> via the RIP[63] bit, making swfilt redundant. Remove the perf unit test
>> that assumes IBS has no hardware-assisted privilege filter.
> 
> Can you add a check for CPU model or capability for this?
> Probably we want to keep this test for older models..

Fixed and posted v3:
https://lore.kernel.org/r/20260508060004.2575-1-ravi.bangoria@amd.com

Thanks Namhyung.

Ravi