(no subject)

[Yinghai Lu]

on x86, before prefill_possible_map(), nr_cpu_ids will be NR_CPUS aka CONFIG_NR_CPUS

add nr_cpus= to set nr_cpu_ids. so we can simulate cpus <=8 on normal config.
instead of change NR_CPUS directly.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/ia64/kernel/acpi.c   |    4 ++--
 arch/x86/kernel/smpboot.c |    7 ++++---
 init/main.c               |   14 ++++++++++++++
 3 files changed, 20 insertions(+), 5 deletions(-)

Index: linux-2.6/init/main.c
===================================================================
--- linux-2.6.orig/init/main.c
+++ linux-2.6/init/main.c
@@ -149,6 +149,20 @@ static int __init nosmp(char *str)
 
 early_param("nosmp", nosmp);
 
+/* this is hard limit */
+static int __init nrcpus(char *str)
+{
+	int nr_cpus;
+
+	get_option(&str, &nr_cpus);
+	if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
+		nr_cpu_ids = nr_cpus;
+
+	return 0;
+}
+
+early_param("nr_cpus", nrcpus);
+
 static int __init maxcpus(char *str)
 {
 	get_option(&str, &setup_max_cpus);
Index: linux-2.6/arch/ia64/kernel/acpi.c
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/acpi.c
+++ linux-2.6/arch/ia64/kernel/acpi.c
@@ -883,8 +883,8 @@ __init void prefill_possible_map(void)
 
 	possible = available_cpus + additional_cpus;
 
-	if (possible > NR_CPUS)
-		possible = NR_CPUS;
+	if (possible > nr_cpu_ids)
+		possible = nr_cpu_ids;
 
 	printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n",
 		possible, max((possible - available_cpus), 0));
Index: linux-2.6/arch/x86/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/smpboot.c
+++ linux-2.6/arch/x86/kernel/smpboot.c
@@ -1213,11 +1213,12 @@ __init void prefill_possible_map(void)
 
 	total_cpus = max_t(int, possible, num_processors + disabled_cpus);
 
-	if (possible > CONFIG_NR_CPUS) {
+	/* nr_cpu_ids could be reduced via nr_cpus= */
+	if (possible > nr_cpu_ids) {
 		printk(KERN_WARNING
 			"%d Processors exceeds NR_CPUS limit of %d\n",
-			possible, CONFIG_NR_CPUS);
-		possible = CONFIG_NR_CPUS;
+			possible, nr_cpu_ids);
+		possible = nr_cpu_ids;
 	}
 
 	printk(KERN_INFO "SMP: Allowing %d CPUs, %d hotplug CPUs\n",

(no subject)

[Yinghai Lu]

not sure it works again, could be bios fix the irq routing dest ?

tested that amd support logical flat too when cpus num <= 8 and even
bsp apic id > 8

so could remove vendor check...

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/kernel/apic/apic.c     |   11 ++---------
 arch/x86/kernel/apic/probe_64.c |   13 ++-----------
 2 files changed, 4 insertions(+), 20 deletions(-)

Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/apic.c
+++ linux-2.6/arch/x86/kernel/apic/apic.c
@@ -1898,15 +1898,8 @@ void __cpuinit generic_processor_info(in
 		max_physical_apicid = apicid;
 
 #ifdef CONFIG_X86_32
-	switch (boot_cpu_data.x86_vendor) {
-	case X86_VENDOR_INTEL:
-		if (num_processors > 8)
-			def_to_bigsmp = 1;
-		break;
-	case X86_VENDOR_AMD:
-		if (max_physical_apicid >= 8)
-			def_to_bigsmp = 1;
-	}
+	if (num_processors > 8)
+		def_to_bigsmp = 1;
 #endif
 
 #if defined(CONFIG_SMP) || defined(CONFIG_X86_64)
Index: linux-2.6/arch/x86/kernel/apic/probe_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/probe_64.c
+++ linux-2.6/arch/x86/kernel/apic/probe_64.c
@@ -67,17 +67,8 @@ void __init default_setup_apic_routing(v
 	}
 #endif
 
-	if (apic == &apic_flat) {
-		switch (boot_cpu_data.x86_vendor) {
-		case X86_VENDOR_INTEL:
-			if (num_processors > 8)
-				apic = &apic_physflat;
-			break;
-		case X86_VENDOR_AMD:
-			if (max_physical_apicid >= 8)
-				apic = &apic_physflat;
-		}
-	}
+	if (apic == &apic_flat && num_processors > 8)
+		apic = &apic_physflat;
 
 	printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
 

(no subject)

[Yinghai Lu]

should use nr_cpu_ids instead of num_processor, in case we have hotplug cpus.

if current only have 8 cpus is up, but if we will have more cpus that
will be hot added later, we should use physical flat at first.

nr_cpu_ids is the total cpus that could be supported.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/kernel/apic/probe_32.c |   20 ++++++++++++++++++--
 arch/x86/kernel/apic/probe_64.c |    3 ++-
 arch/x86/kernel/smpboot.c       |    2 --
 3 files changed, 20 insertions(+), 5 deletions(-)

Index: linux-2.6/arch/x86/kernel/apic/probe_32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/probe_32.c
+++ linux-2.6/arch/x86/kernel/apic/probe_32.c
@@ -52,7 +52,7 @@ static int __init print_ipi_mode(void)
 }
 late_initcall(print_ipi_mode);
 
-void default_setup_apic_routing(void)
+static void local_default_setup_apic_routing(void)
 {
 #ifdef CONFIG_X86_IO_APIC
 	printk(KERN_INFO
@@ -103,7 +103,7 @@ struct apic apic_default = {
 	.init_apic_ldr			= default_init_apic_ldr,
 
 	.ioapic_phys_id_map		= default_ioapic_phys_id_map,
-	.setup_apic_routing		= default_setup_apic_routing,
+	.setup_apic_routing		= local_default_setup_apic_routing,
 	.multi_timer_check		= NULL,
 	.apicid_to_node			= default_apicid_to_node,
 	.cpu_to_logical_apicid		= default_cpu_to_logical_apicid,
@@ -207,6 +207,22 @@ void __init generic_bigsmp_probe(void)
 			apic = &apic_bigsmp;
 			printk(KERN_INFO "Overriding APIC driver with %s\n",
 			       apic->name);
+		}
+	}
+#endif
+}
+
+void default_setup_apic_routing(void)
+{
+#ifdef CONFIG_X86_BIGSMP
+	/*
+	 * make sure we go to bigsmp according to real nr_cpu_ids
+	 */
+	if (!cmdline_apic && apic == &apic_default) {
+		if (nr_cpu_ids > 8) {
+			apic = &apic_bigsmp;
+			printk(KERN_INFO "Overriding APIC driver with %s\n",
+			       apic->name);
 		}
 	}
 #endif
Index: linux-2.6/arch/x86/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/smpboot.c
+++ linux-2.6/arch/x86/kernel/smpboot.c
@@ -1084,9 +1084,7 @@ void __init native_smp_prepare_cpus(unsi
 	set_cpu_sibling_map(0);
 
 	enable_IR_x2apic();
-#ifdef CONFIG_X86_64
 	default_setup_apic_routing();
-#endif
 
 	if (smp_sanity_check(max_cpus) < 0) {
 		printk(KERN_INFO "SMP disabled\n");
Index: linux-2.6/arch/x86/kernel/apic/probe_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/probe_64.c
+++ linux-2.6/arch/x86/kernel/apic/probe_64.c
@@ -67,7 +67,8 @@ void __init default_setup_apic_routing(v
 	}
 #endif
 
-	if (apic == &apic_flat && num_processors > 8)
+	/* not just num_processors, we could have hotplug cpus */
+	if (apic == &apic_flat && nr_cpu_ids > 8)
 		apic = &apic_physflat;
 
 	printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);

(no subject)

[Yinghai Lu]

some systems that have disable cpus entries because same
  BIOS will support 2 sockets and 4 sockets and more at
  same time, BIOS just leave some disable entries, but
  those system do not support cpu hotplug. we don't need
  treat disabled_cpus as hotplug cpus.
so we can make nr_cpu_ids smaller and save more space
  (pcpu data allocations), and could make some systems run
  with logical flat instead of physical flat apic mode

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/kernel/smpboot.c |   39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

Index: linux-2.6/arch/x86/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/smpboot.c
+++ linux-2.6/arch/x86/kernel/smpboot.c
@@ -47,6 +47,7 @@
 #include <linux/bootmem.h>
 #include <linux/err.h>
 #include <linux/nmi.h>
+#include <linux/dmi.h>
 #include <linux/tboot.h>
 
 #include <asm/acpi.h>
@@ -1180,6 +1181,24 @@ static int __init _setup_possible_cpus(c
 }
 early_param("possible_cpus", _setup_possible_cpus);
 
+static __initdata int treat_disabled_cpus_as_hotplug;
+static __init int hotplug_cpus_check(const struct dmi_system_id *d)
+{
+        printk(KERN_NOTICE "%s detected: treat disabled cpus as hotplug ones\n", d->ident);
+        treat_disabled_cpus_as_hotplug = 1;
+
+        return 0;
+}
+
+static struct dmi_system_id hotplug_cpus_dmi_table[] __initdata = {
+        { hotplug_cpus_check, "WHICH VENDOR WHAT SYSTEM",
+                {       DMI_MATCH(DMI_BIOS_VENDOR, "WHAT VENDOR"),
+                        DMI_MATCH(DMI_BIOS_VERSION, "WHAT VER"),
+                }
+        },
+        { } /* NULL entry stops DMI scanning */
+};
+
 
 /*
  * cpu_possible_mask should be static, it cannot change as cpu's
@@ -1206,8 +1225,24 @@ __init void prefill_possible_map(void)
 	if (!num_processors)
 		num_processors = 1;
 
-	if (setup_possible_cpus == -1)
-		possible = num_processors + disabled_cpus;
+	if (setup_possible_cpus == -1) {
+		possible = num_processors;
+		/*
+		 * do we have better way to detect hotplug cpus?
+		 *
+		 * some systems that have disable cpus entries because same
+		 *  BIOS will support 2 sockets and 4 sockets and more at
+		 *  same time, BIOS just leave some disable entries, but
+		 *  those system do not support cpu hotplug. we don't need
+		 *  treat disabled_cpus as hotplug cpus.
+		 * so we can make nr_cpu_ids smaller and save more space
+		 *  (pcpu data allocations), and could make some systems run
+		 *  with logical flat instead of physical flat apic mode
+		 */
+		dmi_check_system(hotplug_cpus_dmi_table);
+		if (treat_disabled_cpus_as_hotplug)
+			possible += disabled_cpus;
+	}
 	else
 		possible = setup_possible_cpus;