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Mark Rutland 6cc145c521 perf print-events: make is_event_supported() more robust 
[ Upstream commit 25412c0364 ]

Currently the perf tool doesn't detect support for extended event types
on Apple M1/M2 systems, and will not auto-expand plain PERF_EVENT_TYPE
hardware events into per-PMU events. This is due to the detection of
extended event types not handling mandatory filters required by the
M1/M2 PMU driver.

PMU drivers and the core perf_events code can require that
perf_event_attr::exclude_* filters are configured in a specific way and
may reject certain configurations of filters, for example:

(a) Many PMUs lack support for any event filtering, and require all
    perf_event_attr::exclude_* bits to be clear. This includes Alpha's
    CPU PMU, and ARM CPU PMUs prior to the introduction of PMUv2 in
    ARMv7,

(b) When /proc/sys/kernel/perf_event_paranoid >= 2, the perf core
    requires that perf_event_attr::exclude_kernel is set.

(c) The Apple M1/M2 PMU requires that perf_event_attr::exclude_guest is
    set as the hardware PMU does not count while a guest is running (but
    might be extended in future to do so).

In is_event_supported(), we try to account for cases (a) and (b), first
attempting to open an event without any filters, and if this fails,
retrying with perf_event_attr::exclude_kernel set. We do not account for
case (c), or any other filters that drivers could theoretically require
to be set.

Thus is_event_supported() will fail to detect support for any events
targeting an Apple M1/M2 PMU, even where events would be supported with
perf_event_attr:::exclude_guest set.

Since commit:

  82fe2e45cd ("perf pmus: Check if we can encode the PMU number in perf_event_attr.type")

... we use is_event_supported() to detect support for extended types,
with the PMU ID encoded into the perf_event_attr::type. As above, on an
Apple M1/M2 system this will always fail to detect that the event is
supported, and consequently we fail to detect support for extended types
even when these are supported, as they have been since commit:

  5c81672865 ("arm_pmu: Add PERF_PMU_CAP_EXTENDED_HW_TYPE capability")

Due to this, the perf tool will not automatically expand plain
PERF_TYPE_HARDWARE events into per-PMU events, even when all the
necessary kernel support is present.

This patch updates is_event_supported() to additionally try opening
events with perf_event_attr::exclude_guest set, allowing support for
events to be detected on Apple M1/M2 systems. I believe that this is
sufficient for all contemporary CPU PMU drivers, though in future it may
be necessary to check for other combinations of filter bits.

I've deliberately changed the check to not expect a specific error code
for missing filters, as today ;the kernel may return a number of
different error codes for missing filters (e.g. -EACCESS, -EINVAL, or
-EOPNOTSUPP) depending on why and where the filter configuration is
rejected, and retrying for any error is more robust.

Note that this does not remove the need for commit:

  a24d9d9dc0 ("perf parse-events: Make legacy events lower priority than sysfs/JSON")

... which is still necessary so that named-pmu/event/ events work on
kernels without extended type support, even if the event name happens to
be the same as a PERF_EVENT_TYPE_HARDWARE event (e.g. as is the case for
the M1/M2 PMU's 'cycles' and 'instructions' events).

Fixes: 82fe2e45cd ("perf pmus: Check if we can encode the PMU number in perf_event_attr.type")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Ian Rogers <irogers@google.com>
Tested-by: James Clark <james.clark@arm.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Cc: Hector Martin <marcan@marcan.st>
Cc: James Clark <james.clark@arm.com>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240126145605.1005472-1-mark.rutland@arm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2024-03-26 18:18:37 -04:00
Documentation dt-bindings: msm: qcom, mdss: Include ommited fam-b compatible 2024-03-26 18:18:33 -04:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
arch powerpc: Force inlining of arch_vmap_p{u/m}d_supported() 2024-03-26 18:18:34 -04:00
block block: fix deadlock between bd_link_disk_holder and partition scan 2024-03-26 18:17:59 -04:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto crypto: algif_hash - Remove bogus SGL free on zero-length error path 2024-02-23 09:51:51 +01:00
drivers mfd: altera-sysmgr: Call of_node_put() only when of_parse_phandle() takes a ref 2024-03-26 18:18:37 -04:00
fs quota: Properly annotate i_dquot arrays with __rcu 2024-03-26 18:18:32 -04:00
include clk: renesas: r8a779g0: Correct PFC/GPIO parent clocks 2024-03-26 18:18:33 -04:00
init update workarounds for gcc "asm goto" issue 2024-02-23 09:51:21 +01:00
io_uring io_uring/net: fix overflow check in io_recvmsg_mshot_prep() 2024-03-26 18:18:01 -04:00
ipc Many singleton patches against the MM code. The patch series which are 2023-11-02 19:38:47 -10:00
kernel bpf: hardcode BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes() 2024-03-26 18:18:27 -04:00
lib net: blackhole_dev: fix build warning for ethh set but not used 2024-03-26 18:18:09 -04:00
mm quota: Properly annotate i_dquot arrays with __rcu 2024-03-26 18:18:32 -04:00
net devlink: Fix length of eswitch inline-mode 2024-03-26 18:18:27 -04:00
rust rust: Ignore preserve-most functions 2024-01-25 15:45:09 -08:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-23 09:51:20 +01:00
scripts gen_compile_commands: fix invalid escape sequence warning 2024-03-26 18:17:51 -04:00
security landlock: Fix asymmetric private inodes referring 2024-03-06 14:53:55 +00:00
sound ASoC: SOF: Add some bounds checking to firmware data 2024-03-26 18:18:34 -04:00
tools perf print-events: make is_event_supported() more robust 2024-03-26 18:18:37 -04:00
usr arch: Remove Itanium (IA-64) architecture 2023-09-11 08:13:17 +00:00
virt KVM/arm64 fixes for 6.7, part #2 2023-12-22 18:03:54 -05:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
…
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: generate kernel.spec in rpmbuild/SPECS/ 2023-10-03 20:49:09 +09:00
.mailmap 12 hotfixes. 2 are cc:stable and the remainder either address post-6.7 2024-01-05 13:46:18 -08:00
.rustfmt.toml rust: add `.rustfmt.toml` 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS 12 hotfixes. 2 are cc:stable and the remainder either address post-6.7 2024-01-05 13:46:18 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS 12 hotfixes. 2 are cc:stable and the remainder either address post-6.7 2024-01-05 13:46:18 -08:00
Makefile Linux 6.7.10 2024-03-15 14:22:41 -04:00
README
…

README 

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 Restructured Text 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.