These patches introduce support for the Activity Monitors Unit (AMU) CPU extension, an optional extension in ARMv8.4 CPUs. This provides performance counters intended for system management use. With the CONFIG_ARM64_AMU_EXTN enabled the kernel is able to safely run a mix of CPUs with and without support for the AMU extension. The AMU capability is unconditionally enabled in the kernel as to allow any late CPU to use the feature: the cpu_enable function will be called for all CPUs that match the criteria, including secondary and hotplugged CPUs, marking this feature as present on that respective CPU (through a per-cpu variable). To be noted that firmware must implement AMU support when running on CPUs that present the activity monitors extension: allow access to the registers from lower exception levels, enable the counters, implement save and restore functionality. More details can be found in the documentation. Given that the activity counters inform on activity on the CPUs, and that not all CPUs might implement the extension, for functional and security reasons, it's best to disable access to the AMU registers from userspace (EL0) and KVM guests. The current series is based on linux-next 20190916. Testing: - Build tested for multiple architectures and defconfigs. - AMU feature detection, EL0 and KVM guest access to AMU registers, feature support in firmware (version 1.5 and later of the ARM Trusted Firmware) was tested on an Armv8-A Base Platform FVP: Architecture Envelope Model [1] (supports version 8.0 to 8.5), with the following configurations: cluster0.has_arm_v8-4=1 cluster1.has_arm_v8-4=1 cluster0.has_amu=1 cluster1.has_amu=1 [1] https://developer.arm.com/tools-and-software/simulation-models/fixed-virtual-platforms Ionela Voinescu (4): arm64: add support for the AMU extension v1 arm64: trap to EL1 accesses to AMU counters from EL0 arm64/kvm: disable access to AMU registers from kvm guests Documentation: arm64: document support for the AMU extension Documentation/arm64/amu.rst | 107 ++++++++++++++++++ Documentation/arm64/booting.rst | 14 +++ Documentation/arm64/cpu-feature-registers.rst | 2 + Documentation/arm64/index.rst | 1 + arch/arm64/Kconfig | 27 +++++ arch/arm64/include/asm/assembler.h | 10 ++ arch/arm64/include/asm/cpucaps.h | 3 +- arch/arm64/include/asm/kvm_arm.h | 7 +- arch/arm64/include/asm/sysreg.h | 44 +++++++ arch/arm64/kernel/cpufeature.c | 71 +++++++++++- arch/arm64/kvm/hyp/switch.c | 13 ++- arch/arm64/kvm/sys_regs.c | 95 +++++++++++++++- arch/arm64/mm/proc.S | 3 + 13 files changed, 386 insertions(+), 11 deletions(-) create mode 100644 Documentation/arm64/amu.rst -- 2.17.1
