From 5f2eb55026c91f8400ab4469aff88b2e201b5616 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 24 May 2010 12:13:17 -0700 Subject: x86: "nosmp" command line option should force the system into UP mode Bits set in cpu_possible_mask prior to the execution of prefill_possible_map() (i.e. when parsing ACPI or MPS tables) would prevent the SMP alternatives logic from switching to UP mode, plus unnecessary setup of per-CPU data for CPUs that can never come online. Additionally, without CONFIG_HOTPLUG_CPU disabled CPUs can never come online, and hence setting cpu_possible_mask bits for them is again a simple waste of resources. Signed-off-by: Jan Beulich LKML-Reference: <201005241913.o4OJDH3Z010874@imap1.linux-foundation.org> Signed-off-by: Andrew Morton Signed-off-by: H. Peter Anvin --- arch/x86/kernel/smpboot.c | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 763d815e27a0..37462f1ddba5 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1215,9 +1215,17 @@ __init void prefill_possible_map(void) if (!num_processors) num_processors = 1; - if (setup_possible_cpus == -1) - possible = num_processors + disabled_cpus; - else + i = setup_max_cpus ?: 1; + if (setup_possible_cpus == -1) { + possible = num_processors; +#ifdef CONFIG_HOTPLUG_CPU + if (setup_max_cpus) + possible += disabled_cpus; +#else + if (possible > i) + possible = i; +#endif + } else possible = setup_possible_cpus; total_cpus = max_t(int, possible, num_processors + disabled_cpus); @@ -1230,11 +1238,23 @@ __init void prefill_possible_map(void) possible = nr_cpu_ids; } +#ifdef CONFIG_HOTPLUG_CPU + if (!setup_max_cpus) +#endif + if (possible > i) { + printk(KERN_WARNING + "%d Processors exceeds max_cpus limit of %u\n", + possible, setup_max_cpus); + possible = i; + } + printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n", possible, max_t(int, possible - num_processors, 0)); for (i = 0; i < possible; i++) set_cpu_possible(i, true); + for (; i < NR_CPUS; i++) + set_cpu_possible(i, false); nr_cpu_ids = possible; } -- cgit v1.2.3-59-g8ed1b