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It seems perf sets the exclude_guest bit because of Intel PEBS implementation which uses a virtual address. IIUC now kernel disables PEBS when it goes to the guest mode regardless of this bit so we don't need to set it explicitly. At least for the other archs/vendors. I found the commit1342798cc1set the exclude_guest for precise_ip in the tool and the commit20b279ddb3added kernel side enforcement which was reverted by commita706d965dclater. Actually it doesn't set the exclude_guest for the default event (cycles:P) already. $ grep -m1 vendor /proc/cpuinfo vendor_id : GenuineIntel $ perf record -e cycles:P true [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.002 MB perf.data (9 samples) ] $ perf evlist -v | tr ',' '\n' | grep -e exclude -e precise precise_ip: 3 But having lower 'p' modifier set the bit for some reason. $ perf record -e cycles:pp true [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.002 MB perf.data (9 samples) ] $ perf evlist -v | tr ',' '\n' | grep -e exclude -e precise precise_ip: 2 exclude_guest: 1 Actually AMD IBS suffers from this because it doesn't support excludes and having this bit effectively disables new features in the current implementation (due to the missing feature check). $ grep -m1 vendor /proc/cpuinfo vendor_id : AuthenticAMD $ perf record -W -e cycles:p -vv true 2>&1 | grep switching switching off PERF_FORMAT_LOST support switching off weight struct support switching off bpf_event switching off ksymbol switching off cloexec flag switching off mmap2 switching off exclude_guest, exclude_host By not setting exclude_guest, we can fix this inconsistency and the troubles. Reviewed-by: Ian Rogers <irogers@google.com> Reviewed-by: James Clark <james.clark@linaro.org> Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com> Acked-by: Kan Liang <kan.liang@linux.intel.com> Cc: James Clark <james.clark@arm.com> Cc: Atish Patra <atishp@atishpatra.org> Cc: Mingwei Zhang <mizhang@google.com> Cc: Kajol Jain <kjain@linux.ibm.com> Cc: Thomas Richter <tmricht@linux.ibm.com> Cc: Palmer Dabbelt <palmer@rivosinc.com> Link: https://lore.kernel.org/r/20241016062359.264929-5-namhyung@kernel.org Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.