Commit 14cb6dcf authored by Vivek Goyal's avatar Vivek Goyal Committed by H. Peter Anvin

x86, boot: Wait for boot cpu to show up if nr_cpus limit is about to hit

nr_cpus allows one to specify number of possible cpus in the system.
Current assumption seems to be that first cpu to show up is boot cpu
and this assumption will be broken in kdump scenario where we can be
booting on a non boot cpu with nr_cpus=1.

It might happen that first cpu we parse is not the cpu we boot on and
later we ignore boot cpu. Though code later seems to recognize this
anomaly and forcibly sets boot cpu in physical cpu map with following
warning.

if (!physid_isset(hard_smp_processor_id(), phys_cpu_present_map)) {
        printk(KERN_WARNING
                "weird, boot CPU (#%d) not listed by the BIOS.\n",
                hard_smp_processor_id());

        physid_set(hard_smp_processor_id(), phys_cpu_present_map);
}

This patch waits for boot cpu to show up and starts ignoring the cpus
once we have hit (nr_cpus - 1) number of cpus. So effectively we are
reserving one slot out of nr_cpus for boot cpu explicitly.
Signed-off-by: default avatarVivek Goyal <vgoyal@redhat.com>
Acked-by: default avatarYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/20110708171926.GF2930@redhat.comSigned-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent fe0d4220
...@@ -1943,10 +1943,28 @@ void disconnect_bsp_APIC(int virt_wire_setup) ...@@ -1943,10 +1943,28 @@ void disconnect_bsp_APIC(int virt_wire_setup)
void __cpuinit generic_processor_info(int apicid, int version) void __cpuinit generic_processor_info(int apicid, int version)
{ {
int cpu; int cpu, max = nr_cpu_ids;
bool boot_cpu_detected = physid_isset(boot_cpu_physical_apicid,
phys_cpu_present_map);
/*
* If boot cpu has not been detected yet, then only allow upto
* nr_cpu_ids - 1 processors and keep one slot free for boot cpu
*/
if (!boot_cpu_detected && num_processors >= nr_cpu_ids - 1 &&
apicid != boot_cpu_physical_apicid) {
int thiscpu = max + disabled_cpus - 1;
pr_warning(
"ACPI: NR_CPUS/possible_cpus limit of %i almost"
" reached. Keeping one slot for boot cpu."
" Processor %d/0x%x ignored.\n", max, thiscpu, apicid);
disabled_cpus++;
return;
}
if (num_processors >= nr_cpu_ids) { if (num_processors >= nr_cpu_ids) {
int max = nr_cpu_ids;
int thiscpu = max + disabled_cpus; int thiscpu = max + disabled_cpus;
pr_warning( pr_warning(
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment