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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/arm64/perf.rst | |
parent | Initial commit. (diff) | |
download | linux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.tar.xz linux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/arm64/perf.rst | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/Documentation/arm64/perf.rst b/Documentation/arm64/perf.rst new file mode 100644 index 000000000..9c76a97ba --- /dev/null +++ b/Documentation/arm64/perf.rst @@ -0,0 +1,88 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================== +Perf Event Attributes +===================== + +:Author: Andrew Murray <andrew.murray@arm.com> +:Date: 2019-03-06 + +exclude_user +------------ + +This attribute excludes userspace. + +Userspace always runs at EL0 and thus this attribute will exclude EL0. + + +exclude_kernel +-------------- + +This attribute excludes the kernel. + +The kernel runs at EL2 with VHE and EL1 without. Guest kernels always run +at EL1. + +For the host this attribute will exclude EL1 and additionally EL2 on a VHE +system. + +For the guest this attribute will exclude EL1. Please note that EL2 is +never counted within a guest. + + +exclude_hv +---------- + +This attribute excludes the hypervisor. + +For a VHE host this attribute is ignored as we consider the host kernel to +be the hypervisor. + +For a non-VHE host this attribute will exclude EL2 as we consider the +hypervisor to be any code that runs at EL2 which is predominantly used for +guest/host transitions. + +For the guest this attribute has no effect. Please note that EL2 is +never counted within a guest. + + +exclude_host / exclude_guest +---------------------------- + +These attributes exclude the KVM host and guest, respectively. + +The KVM host may run at EL0 (userspace), EL1 (non-VHE kernel) and EL2 (VHE +kernel or non-VHE hypervisor). + +The KVM guest may run at EL0 (userspace) and EL1 (kernel). + +Due to the overlapping exception levels between host and guests we cannot +exclusively rely on the PMU's hardware exception filtering - therefore we +must enable/disable counting on the entry and exit to the guest. This is +performed differently on VHE and non-VHE systems. + +For non-VHE systems we exclude EL2 for exclude_host - upon entering and +exiting the guest we disable/enable the event as appropriate based on the +exclude_host and exclude_guest attributes. + +For VHE systems we exclude EL1 for exclude_guest and exclude both EL0,EL2 +for exclude_host. Upon entering and exiting the guest we modify the event +to include/exclude EL0 as appropriate based on the exclude_host and +exclude_guest attributes. + +The statements above also apply when these attributes are used within a +non-VHE guest however please note that EL2 is never counted within a guest. + + +Accuracy +-------- + +On non-VHE hosts we enable/disable counters on the entry/exit of host/guest +transition at EL2 - however there is a period of time between +enabling/disabling the counters and entering/exiting the guest. We are +able to eliminate counters counting host events on the boundaries of guest +entry/exit when counting guest events by filtering out EL2 for +exclude_host. However when using !exclude_hv there is a small blackout +window at the guest entry/exit where host events are not captured. + +On VHE systems there are no blackout windows. |