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In some cases, it may be necessary to restrict opening PMU events to a subset of CPUs. E.g. Unified Memory Controller (UMC) PMUs are specific to each active memory channel and the MSR address space for the PERF_CTL and PERF_CTR registers is reused on each socket. Thus, opening events for a specific UMC PMU should be restricted to CPUs belonging to the same socket as that of the UMC. The "cpumask" of the PMU should also reflect this accordingly. Uncore PMUs which require this can use the new group attribute in struct amd_uncore_pmu to set a valid group ID during the scan() phase. Later, during init(), an uncore context for a CPU will be unavailable if the group ID does not match. Signed-off-by: Sandipan Das <sandipan.das@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/937d6d71010a48ea4e069f4904b3116a5f99ecdf.1696425185.git.sandipan.das@amd.com