On Fri, Dec 03, 2021 at 04:20:32PM -0800, Atish Patra wrote: > Currently, sparse hartid is not supported for Linux RISC-V for the following > reasons. > 1. Both spinwait and ordered booting method uses __cpu_up_stack/task_pointer > which is an array size of NR_CPUs. > 2. During early booting, any hartid greater than NR_CPUs are not booted at all. > 3. riscv_cpuid_to_hartid_mask uses struct cpumask for generating hartid bitmap. > 4. SBI v0.2 implementation uses NR_CPUs as the maximum hartid number while > generating hartmask. > > In order to support sparse hartid, the hartid & NR_CPUS needs to be disassociated > which was logically incorrect anyways. NR_CPUs represent the maximum logical| > CPU id configured in the kernel while the hartid represent the physical hartid > stored in mhartid CSR defined by the privilege specification. Thus, hartid > can have much greater value than logical cpuid. We already have a couple of architectures with logical to physical CPU id maps. See cpu_logical_map. Can we make that common and use it here? That would also possibly allow for common populating the map from DT. Rob
