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Subject[PATCH 05/10] x86: Convert x86_cpu_to_apicid to be a per cpu variable (v3)
This patch converts the x86_cpu_to_apicid array to be a per
cpu variable. This saves sizeof(apicid) * NR unused cpus.
Access is mostly from startup and CPU HOTPLUG functions.

MP_processor_info() is one of the functions that require access
to the x86_cpu_to_apicid array before the per_cpu data area is
setup. For this case, a pointer to the __initdata array is
initialized in setup_arch() and removed in smp_prepare_cpus()
after the per_cpu data area is initialized.

A second change is included to change the initial array value
of ARCH i386 from 0xff to BAD_APICID to be consistent with
ARCH x86_64.

Signed-off-by: Mike Travis <travis@sgi.com>
---
arch/i386/kernel/acpi/boot.c | 2 +-
arch/i386/kernel/smp.c | 2 +-
arch/i386/kernel/smpboot.c | 22 +++++++++++++++-------
arch/x86_64/kernel/genapic.c | 15 ++++++++++++---
arch/x86_64/kernel/genapic_flat.c | 2 +-
arch/x86_64/kernel/mpparse.c | 15 +++++++++++++--
arch/x86_64/kernel/setup.c | 5 +++++
arch/x86_64/kernel/smpboot.c | 23 ++++++++++++++++++++++-
arch/x86_64/mm/numa.c | 2 +-
include/asm-i386/smp.h | 6 ++++--
include/asm-x86_64/ipi.h | 2 +-
include/asm-x86_64/smp.h | 6 ++++--
12 files changed, 80 insertions(+), 22 deletions(-)
--- a/arch/i386/kernel/acpi/boot.c
+++ b/arch/i386/kernel/acpi/boot.c
@@ -555,7 +555,7 @@

int acpi_unmap_lsapic(int cpu)
{
- x86_cpu_to_apicid[cpu] = -1;
+ per_cpu(x86_cpu_to_apicid, cpu) = -1;
cpu_clear(cpu, cpu_present_map);
num_processors--;

--- a/arch/i386/kernel/smp.c
+++ b/arch/i386/kernel/smp.c
@@ -673,7 +673,7 @@
int i;

for (i = 0; i < NR_CPUS; i++) {
- if (x86_cpu_to_apicid[i] == apic_id)
+ if (per_cpu(x86_cpu_to_apicid, i) == apic_id)
return i;
}
return -1;
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -92,9 +92,17 @@
struct cpuinfo_x86 cpu_data[NR_CPUS] __cacheline_aligned;
EXPORT_SYMBOL(cpu_data);

-u8 x86_cpu_to_apicid[NR_CPUS] __read_mostly =
- { [0 ... NR_CPUS-1] = 0xff };
-EXPORT_SYMBOL(x86_cpu_to_apicid);
+/*
+ * The following static array is used during kernel startup
+ * and the x86_cpu_to_apicid_ptr contains the address of the
+ * array during this time. Is it zeroed when the per_cpu
+ * data area is removed.
+ */
+u8 x86_cpu_to_apicid_init[NR_CPUS] __initdata =
+ { [0 ... NR_CPUS-1] = BAD_APICID };
+void *x86_cpu_to_apicid_ptr;
+DEFINE_PER_CPU(u8, x86_cpu_to_apicid) = BAD_APICID;
+EXPORT_PER_CPU_SYMBOL(x86_cpu_to_apicid);

u8 apicid_2_node[MAX_APICID];

@@ -804,7 +812,7 @@

irq_ctx_init(cpu);

- x86_cpu_to_apicid[cpu] = apicid;
+ per_cpu(x86_cpu_to_apicid, cpu) = apicid;
/*
* This grunge runs the startup process for
* the targeted processor.
@@ -866,7 +874,7 @@
cpu_clear(cpu, cpu_initialized); /* was set by cpu_init() */
cpucount--;
} else {
- x86_cpu_to_apicid[cpu] = apicid;
+ per_cpu(x86_cpu_to_apicid, cpu) = apicid;
cpu_set(cpu, cpu_present_map);
}

@@ -915,7 +923,7 @@
struct warm_boot_cpu_info info;
int apicid, ret;

- apicid = x86_cpu_to_apicid[cpu];
+ apicid = per_cpu(x86_cpu_to_apicid, cpu);
if (apicid == BAD_APICID) {
ret = -ENODEV;
goto exit;
@@ -965,7 +973,7 @@

boot_cpu_physical_apicid = GET_APIC_ID(apic_read(APIC_ID));
boot_cpu_logical_apicid = logical_smp_processor_id();
- x86_cpu_to_apicid[0] = boot_cpu_physical_apicid;
+ per_cpu(x86_cpu_to_apicid, 0) = boot_cpu_physical_apicid;

current_thread_info()->cpu = 0;

--- a/arch/x86_64/kernel/mpparse.c
+++ b/arch/x86_64/kernel/mpparse.c
@@ -86,7 +86,7 @@
return sum & 0xFF;
}

-static void __cpuinit MP_processor_info (struct mpc_config_processor *m)
+static void __cpuinit MP_processor_info(struct mpc_config_processor *m)
{
int cpu;
cpumask_t tmp_map;
@@ -123,7 +123,18 @@
cpu = 0;
}
bios_cpu_apicid[cpu] = m->mpc_apicid;
- x86_cpu_to_apicid[cpu] = m->mpc_apicid;
+ /*
+ * We get called early in the the start_kernel initialization
+ * process when the per_cpu data area is not yet setup, so we
+ * use a static array that is removed after the per_cpu data
+ * area is created.
+ */
+ if (x86_cpu_to_apicid_ptr) {
+ u8 *x86_cpu_to_apicid = (u8 *)x86_cpu_to_apicid_ptr;
+ x86_cpu_to_apicid[cpu] = m->mpc_apicid;
+ } else {
+ per_cpu(x86_cpu_to_apicid, cpu) = m->mpc_apicid;
+ }

cpu_set(cpu, cpu_possible_map);
cpu_set(cpu, cpu_present_map);
--- a/arch/x86_64/kernel/smpboot.c
+++ b/arch/x86_64/kernel/smpboot.c
@@ -701,7 +701,7 @@
clear_node_cpumask(cpu); /* was set by numa_add_cpu */
cpu_clear(cpu, cpu_present_map);
cpu_clear(cpu, cpu_possible_map);
- x86_cpu_to_apicid[cpu] = BAD_APICID;
+ per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID;
return -EIO;
}

@@ -848,6 +848,26 @@
}

/*
+ * Copy apicid's found by MP_processor_info from initial array to the per cpu
+ * data area. The x86_cpu_to_apicid_init array is then expendable and the
+ * x86_cpu_to_apicid_ptr is zeroed indicating that the static array is no
+ * longer available.
+ */
+void __init smp_set_apicids(void)
+{
+ int cpu;
+
+ for_each_cpu_mask(cpu, cpu_possible_map) {
+ if (per_cpu_offset(cpu))
+ per_cpu(x86_cpu_to_apicid, cpu) =
+ x86_cpu_to_apicid_init[cpu];
+ }
+
+ /* indicate the static array will be going away soon */
+ x86_cpu_to_apicid_ptr = NULL;
+}
+
+/*
* Prepare for SMP bootup. The MP table or ACPI has been read
* earlier. Just do some sanity checking here and enable APIC mode.
*/
@@ -856,6 +876,7 @@
nmi_watchdog_default();
current_cpu_data = boot_cpu_data;
current_thread_info()->cpu = 0; /* needed? */
+ smp_set_apicids();
set_cpu_sibling_map(0);

if (smp_sanity_check(max_cpus) < 0) {
--- a/arch/x86_64/mm/numa.c
+++ b/arch/x86_64/mm/numa.c
@@ -612,7 +612,7 @@
{
int i;
for (i = 0; i < NR_CPUS; i++) {
- u8 apicid = x86_cpu_to_apicid[i];
+ u8 apicid = x86_cpu_to_apicid_init[i];
if (apicid == BAD_APICID)
continue;
if (apicid_to_node[apicid] == NUMA_NO_NODE)
--- a/include/asm-i386/smp.h
+++ b/include/asm-i386/smp.h
@@ -39,9 +39,11 @@
extern void unlock_ipi_call_lock(void);

#define MAX_APICID 256
-extern u8 x86_cpu_to_apicid[];
+extern u8 __initdata x86_cpu_to_apicid_init[];
+extern void *x86_cpu_to_apicid_ptr;
+DECLARE_PER_CPU(u8, x86_cpu_to_apicid);

-#define cpu_physical_id(cpu) x86_cpu_to_apicid[cpu]
+#define cpu_physical_id(cpu) per_cpu(x86_cpu_to_apicid, cpu)

extern void set_cpu_sibling_map(int cpu);

--- a/include/asm-x86_64/ipi.h
+++ b/include/asm-x86_64/ipi.h
@@ -119,7 +119,7 @@
*/
local_irq_save(flags);
for_each_cpu_mask(query_cpu, mask) {
- __send_IPI_dest_field(x86_cpu_to_apicid[query_cpu],
+ __send_IPI_dest_field(per_cpu(x86_cpu_to_apicid, query_cpu),
vector, APIC_DEST_PHYSICAL);
}
local_irq_restore(flags);
--- a/include/asm-x86_64/smp.h
+++ b/include/asm-x86_64/smp.h
@@ -85,7 +85,9 @@
* Some lowlevel functions might want to know about
* the real APIC ID <-> CPU # mapping.
*/
-extern u8 x86_cpu_to_apicid[NR_CPUS]; /* physical ID */
+extern u8 __initdata x86_cpu_to_apicid_init[];
+extern void *x86_cpu_to_apicid_ptr;
+DECLARE_PER_CPU(u8, x86_cpu_to_apicid); /* physical ID */
extern u8 bios_cpu_apicid[];

static inline int cpu_present_to_apicid(int mps_cpu)
@@ -116,7 +118,7 @@
}

#ifdef CONFIG_SMP
-#define cpu_physical_id(cpu) x86_cpu_to_apicid[cpu]
+#define cpu_physical_id(cpu) per_cpu(x86_cpu_to_apicid, cpu)
#else
#define cpu_physical_id(cpu) boot_cpu_id
#endif /* !CONFIG_SMP */
--- a/arch/x86_64/kernel/genapic_flat.c
+++ b/arch/x86_64/kernel/genapic_flat.c
@@ -172,7 +172,7 @@
*/
cpu = first_cpu(cpumask);
if ((unsigned)cpu < NR_CPUS)
- return x86_cpu_to_apicid[cpu];
+ return per_cpu(x86_cpu_to_apicid, cpu);
else
return BAD_APICID;
}
--- a/arch/x86_64/kernel/genapic.c
+++ b/arch/x86_64/kernel/genapic.c
@@ -24,10 +24,19 @@
#include <acpi/acpi_bus.h>
#endif

-/* which logical CPU number maps to which CPU (physical APIC ID) */
-u8 x86_cpu_to_apicid[NR_CPUS] __read_mostly
+/*
+ * which logical CPU number maps to which CPU (physical APIC ID)
+ *
+ * The following static array is used during kernel startup
+ * and the x86_cpu_to_apicid_ptr contains the address of the
+ * array during this time. Is it zeroed when the per_cpu
+ * data area is removed.
+ */
+u8 x86_cpu_to_apicid_init[NR_CPUS] __initdata
= { [0 ... NR_CPUS-1] = BAD_APICID };
-EXPORT_SYMBOL(x86_cpu_to_apicid);
+void *x86_cpu_to_apicid_ptr;
+DEFINE_PER_CPU(u8, x86_cpu_to_apicid) = BAD_APICID;
+EXPORT_PER_CPU_SYMBOL(x86_cpu_to_apicid);

struct genapic __read_mostly *genapic = &apic_flat;

--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -276,6 +276,11 @@

dmi_scan_machine();

+#ifdef CONFIG_SMP
+ /* setup to use the static apicid table during kernel startup */
+ x86_cpu_to_apicid_ptr = (void *)&x86_cpu_to_apicid_init;
+#endif
+
#ifdef CONFIG_ACPI
/*
* Initialize the ACPI boot-time table parser (gets the RSDP and SDT).
--
-
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