arm64: Fix behavior of maxcpus=N (44dbcc93) · Commits · 戴 / test

maxcpu=n sets the number of CPUs activated at boot time to a max of n, but allowing the remaining CPUs to be brought up later if the user decides to do so. However, on arm64 due to various reasons, we disallowed hotplugging CPUs beyond n, by marking them not present. Now that we have checks in place to make sure the hotplugged CPUs have compatible features with system and requires no new errata, relax the restriction. Cc: Will Deacon <will.deacon@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: James Morse <james.morse@arm.com> Reviewed-by:

Catalin Marinas <catalin.marinas@arm.com> Signed-off-by:

Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by:

Will Deacon <will.deacon@arm.com>

arch/arm64/kernel/smp.c

+1 −17

Original line number	Diff line number	Diff line
		@@ -689,33 +689,18 @@ void __init smp_init_cpus(void)
		void __init smp_prepare_cpus(unsigned int max_cpus)
		{
		int err;
		unsigned int cpu, ncores = num_possible_cpus();
		unsigned int cpu;

		init_cpu_topology();

		smp_store_cpu_info(smp_processor_id());

		/*
		* are we trying to boot more cores than exist?
		*/
		if (max_cpus > ncores)
		max_cpus = ncores;

		/* Don't bother if we're effectively UP */
		if (max_cpus <= 1)
		return;

		/*
		* Initialise the present map (which describes the set of CPUs
		* actually populated at the present time) and release the
		* secondaries from the bootloader.
		*
		* Make sure we online at most (max_cpus - 1) additional CPUs.
		*/
		max_cpus--;
		for_each_possible_cpu(cpu) {
		if (max_cpus == 0)
		break;

		if (cpu == smp_processor_id())
		continue;
		@@ -728,7 +713,6 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
		continue;

		set_cpu_present(cpu, true);
		max_cpus--;
		}
		}

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