Hi Alex, On 27/10/2020 17:26, Alexandru Elisei wrote: > Detect Statistical Profiling Extension (SPE) support using the cpufeatures > framework. The presence of SPE is reported via the ARM64_SPE capability. > > The feature will be necessary for emulating SPE in KVM, because KVM needs > that all CPUs have SPE hardware to avoid scheduling a VCPU on a CPU without > support. For this reason, the feature type ARM64_CPUCAP_SYSTEM_FEATURE has > been selected to disallow hotplugging a CPU which doesn't support SPE. Can you mention the existing driver in the commit message? Surprisingly it doesn't use cpufeature at all. It looks like arm_spe_pmu_dev_init() goes out of its way to support mismatched systems. (otherwise the significance of the new behaviour isn't clear!) I read it as: the host is fine with mismatched systems, and the existing drivers supports this. But KVM is not. After this patch you can't make the system mismatched 'late'. Thanks, James _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
