From: Stefan Assmann <sassmann@redhat.com>
Date: Tue, 10 Nov 2009 09:13:01 -0500
Subject: [acpi] support physical cpu hotplug on x86_64
Message-id: <4AF92E9D.8010607@redhat.com>
Patchwork-id: 21342
O-Subject: [RHEL 5.5 PATCH v3] Support physical cpu hotplug for x86_64
Bugzilla: 516999
RH-Acked-by: Danny Feng <dfeng@redhat.com>
RH-Acked-by: Dean Nelson <dnelson@redhat.com>

Bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=516999

Description:
This patch enables ACPI based physical CPU hotplug support for x86_64.
Implements acpi_map_lsapic() to hot-add a CPU. Hot-removing is not
supported so far. Added #ifdef CONFIG_X86_64 around the code to make
sure it's only executed on x86_64.

Comment #2 from Hitachi:
In the latest upstream kernel, the following changes have been
applied on top of the original patch (commit 73fea175).

  1. change buffer name with the latest ACPI spec
  2. change variable name and structure name
  3. add processing to allocate cpumask structure on given node

1 and 2 are just name change, not important. 3 is code excuted by
CONFIG_CPUMASK_OFFSTACK=y, but it is not set in RHEL.

So we don't backport these changes.

Upstream Status:
http://git.kernel.org/linus/73fea175303926055440c06bc8894f0c5c58afc8

Brew Build:
https://brewweb.devel.redhat.com/taskinfo?taskID=2067608

Test Status:
Patch supplied and tested by Hitachi. For verification I've tested cpu
hot-add by utilizing kvms cpu_set capability (using kvm from F11).

  Stefan

diff --git a/arch/i386/kernel/acpi/boot.c b/arch/i386/kernel/acpi/boot.c
index dfa658b..7365930 100644
--- a/arch/i386/kernel/acpi/boot.c
+++ b/arch/i386/kernel/acpi/boot.c
@@ -26,6 +26,7 @@
 #include <linux/init.h>
 #include <linux/acpi.h>
 #include <linux/efi.h>
+#include <linux/cpumask.h>
 #include <linux/module.h>
 #include <linux/dmi.h>
 #include <linux/irq.h>
@@ -504,11 +505,69 @@ EXPORT_SYMBOL(acpi_register_gsi);
  *  ACPI based hotplug support for CPU
  */
 #ifdef CONFIG_ACPI_HOTPLUG_CPU
+
+#ifdef	CONFIG_X86_64
+int acpi_map_lsapic(acpi_handle handle, int *pcpu)
+{
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *obj;
+	struct acpi_table_lapic *lapic;
+	cpumask_t tmp_map, new_map;
+	u8 physid;
+	int cpu;
+
+	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_MAT", NULL, &buffer)))
+		return -EINVAL;
+
+	if (!buffer.length || !buffer.pointer)
+		return -EINVAL;
+
+	obj = buffer.pointer;
+	if (obj->type != ACPI_TYPE_BUFFER ||
+	    obj->buffer.length < sizeof(*lapic)) {
+		kfree(buffer.pointer);
+		return -EINVAL;
+	}
+
+	lapic = (struct acpi_table_lapic *)obj->buffer.pointer;
+
+	if ((lapic->header.type != ACPI_MADT_LAPIC) ||
+	    (!lapic->flags.enabled)) {
+		kfree(buffer.pointer);
+		return -EINVAL;
+	}
+
+	physid = lapic->id;
+
+	kfree(buffer.pointer);
+	buffer.length = ACPI_ALLOCATE_BUFFER;
+	buffer.pointer = NULL;
+
+	tmp_map = cpu_present_map;
+	mp_register_lapic(physid, lapic->flags.enabled);
+
+	/*
+	 * If mp_register_lapic successfully generates a new logical cpu
+	 * number, then the following will get us exactly what was mapped
+	 */
+	cpus_andnot(new_map, cpu_present_map, tmp_map);
+	if (cpus_empty(new_map)) {
+		printk ("Unable to map lapic to logical cpu number\n");
+		return -EINVAL;
+	}
+
+	cpu = first_cpu(new_map);
+
+	*pcpu = cpu;
+	return 0;
+}
+#else	/* X86 */
 int acpi_map_lsapic(acpi_handle handle, int *pcpu)
 {
 	/* TBD */
 	return -EINVAL;
 }
+#endif	/* CONFIG_X86_64 */
 
 EXPORT_SYMBOL(acpi_map_lsapic);
 
diff --git a/arch/i386/kernel/mpparse.c b/arch/i386/kernel/mpparse.c
index 40f4daf..8ecee55 100644
--- a/arch/i386/kernel/mpparse.c
+++ b/arch/i386/kernel/mpparse.c
@@ -68,7 +68,7 @@ unsigned int def_to_bigsmp = 0;
 /* Processor that is doing the boot up */
 unsigned int boot_cpu_physical_apicid = -1U;
 /* Internal processor count */
-static unsigned int __devinitdata num_processors;
+unsigned int __cpuinitdata num_processors;
 
 /* Bitmask of physically existing CPUs */
 physid_mask_t phys_cpu_present_map;
diff --git a/arch/x86_64/kernel/mpparse.c b/arch/x86_64/kernel/mpparse.c
index a3f7db8..2f720ba 100644
--- a/arch/x86_64/kernel/mpparse.c
+++ b/arch/x86_64/kernel/mpparse.c
@@ -64,7 +64,7 @@ unsigned long mp_lapic_addr = 0;
 /* Processor that is doing the boot up */
 unsigned int boot_cpu_id = -1U;
 /* Internal processor count */
-unsigned int num_processors __initdata = 0;
+unsigned int num_processors __cpuinitdata = 0;
 
 unsigned disabled_cpus __cpuinitdata;
 
diff --git a/include/asm-i386/smp.h b/include/asm-i386/smp.h
index 70fd693..d46581f 100644
--- a/include/asm-i386/smp.h
+++ b/include/asm-i386/smp.h
@@ -95,6 +95,7 @@ static __inline int logical_smp_processor_id(void)
 
 extern int __cpu_disable(void);
 extern void __cpu_die(unsigned int cpu);
+extern unsigned int num_processors;
 #endif /* !__ASSEMBLY__ */
 
 #else /* CONFIG_SMP */