The patch titled x86: "nosmp" command line option should force the system into UP mode has been added to the -mm tree. Its filename is x86-nosmp-command-line-option-should-force-the-system-into-up-mode.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: x86: "nosmp" command line option should force the system into UP mode From: "Jan Beulich" <JBeulich@xxxxxxxxxx> 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 <jbeulich@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/smpboot.c | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) diff -puN arch/x86/kernel/smpboot.c~x86-nosmp-command-line-option-should-force-the-system-into-up-mode arch/x86/kernel/smpboot.c --- a/arch/x86/kernel/smpboot.c~x86-nosmp-command-line-option-should-force-the-system-into-up-mode +++ a/arch/x86/kernel/smpboot.c @@ -1214,9 +1214,17 @@ __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); @@ -1229,11 +1237,23 @@ __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; } _ Patches currently in -mm which might be from JBeulich@xxxxxxxxxx are linux-next.patch drivers-base-cpuc-fix-the-output-from-sys-devices-system-cpu-offline.patch x86-nosmp-command-line-option-should-force-the-system-into-up-mode.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html