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Date: Tue, 13 Jan 2009 19:38:12 +0900
From: Tejun Heo <tj@...nel.org>
To: ebiederm@...ssion.com, cl@...ux-foundation.org,
rusty@...tcorp.com.au, mingo@...e.hu, travis@....com,
linux-kernel@...r.kernel.org, hpa@...or.com,
akpm@...ux-foundation.org, steiner@....com, hugh@...itas.com
Cc: Tejun Heo <tj@...nel.org>
Subject: [PATCH 08/13] x86_64: fold pda into percpu area on SMP
Currently pdas and percpu areas are allocated separately. %gs points
to local pda and percpu area can be reached using pda->data_offset.
This patch folds pda into percpu area.
Due to strange gcc requirement, pda needs to be at the beginning of
the percpu area so that pda->stack_canary is at %gs:40. To achieve
this, a new percpu output section macro - PERCPU_VADDR_PREALLOC() - is
added and used to reserve pda sized chunk at the start of the percpu
area.
After this change, for boot cpu, %gs first points to pda in the
data.init area and later during setup_per_cpu_areas() gets updated to
point to the actual pda. This means that setup_per_cpu_areas() need
to reload %gs for CPU0 while clearing pda area for other cpus as cpu0
already has modified it when control reaches setup_per_cpu_areas().
This patch also removes now unnecessary get_local_pda() and its call
sites.
A lot of this patch is taken from Mike Travis' "x86_64: Fold pda into
per cpu area" patch.
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Mike Travis <travis@....com>
---
arch/x86/include/asm/percpu.h | 8 ++++
arch/x86/include/asm/smp.h | 2 -
arch/x86/kernel/asm-offsets_64.c | 1 +
arch/x86/kernel/cpu/common.c | 6 +--
arch/x86/kernel/head64.c | 8 ++++-
arch/x86/kernel/head_64.S | 15 ++++++--
arch/x86/kernel/setup_percpu.c | 65 ++++++++++++++----------------------
arch/x86/kernel/smpboot.c | 60 +---------------------------------
arch/x86/kernel/vmlinux_64.lds.S | 6 ++-
arch/x86/xen/smp.c | 10 ------
include/asm-generic/vmlinux.lds.h | 25 +++++++++++++-
11 files changed, 83 insertions(+), 123 deletions(-)
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index df644f3..0ed77cf 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -1,6 +1,14 @@
#ifndef _ASM_X86_PERCPU_H
#define _ASM_X86_PERCPU_H
+#ifndef __ASSEMBLY__
+#ifdef CONFIG_X86_64
+extern void load_pda_offset(int cpu);
+#else
+static inline void load_pda_offset(int cpu) { }
+#endif
+#endif
+
#ifdef CONFIG_X86_64
#include <linux/compiler.h>
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index d12811c..288a89e 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -25,8 +25,6 @@ extern cpumask_t cpu_callin_map;
extern void (*mtrr_hook)(void);
extern void zap_low_mappings(void);
-extern int __cpuinit get_local_pda(int cpu);
-
extern int smp_num_siblings;
extern unsigned int num_processors;
extern cpumask_t cpu_initialized;
diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index 1d41d3f..f8d1b04 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -56,6 +56,7 @@ int main(void)
ENTRY(cpunumber);
ENTRY(irqstackptr);
ENTRY(data_offset);
+ DEFINE(pda_size, sizeof(struct x8664_pda));
BLANK();
#undef ENTRY
#ifdef CONFIG_PARAVIRT
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 5c3d6b3..cdd419a 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -873,10 +873,8 @@ void __cpuinit pda_init(int cpu)
/* Setup up data that may be needed in __get_free_pages early */
loadsegment(fs, 0);
loadsegment(gs, 0);
- /* Memory clobbers used to order PDA accessed */
- mb();
- wrmsrl(MSR_GS_BASE, pda);
- mb();
+
+ load_pda_offset(cpu);
pda->cpunumber = cpu;
pda->irqcount = -1;
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 84b96b9..ff39bdd 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -26,12 +26,18 @@
#include <asm/bios_ebda.h>
#include <asm/trampoline.h>
-/* boot cpu pda, referenced by head_64.S to initialize %gs for boot CPU */
+#ifndef CONFIG_SMP
+/* boot cpu pda, referenced by head_64.S to initialize %gs on UP */
struct x8664_pda _boot_cpu_pda __read_mostly;
+#endif
void __init x86_64_init_pda(void)
{
+#ifdef CONFIG_SMP
+ cpu_pda(0) = (void *)__per_cpu_load;
+#else
cpu_pda(0) = &_boot_cpu_pda;
+#endif
cpu_pda(0)->data_offset =
(unsigned long)(__per_cpu_load - __per_cpu_start);
pda_init(0);
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 3f56a8f..519185f 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -245,10 +245,13 @@ ENTRY(secondary_startup_64)
/* Set up %gs.
*
- * %gs should point to the pda. For initial boot, make %gs point
- * to the _boot_cpu_pda in data section. For a secondary CPU,
- * initial_gs should be set to its pda address before the CPU runs
- * this code.
+ * On SMP, %gs should point to the per-cpu area. For initial
+ * boot, make %gs point to the init data section. For a
+ * secondary CPU,initial_gs should be set to its pda address
+ * before the CPU runs this code.
+ *
+ * On UP, initial_gs points to _boot_cpu_pda and doesn't
+ * change.
*/
movl $MSR_GS_BASE,%ecx
movq initial_gs(%rip),%rax
@@ -278,7 +281,11 @@ ENTRY(secondary_startup_64)
ENTRY(initial_code)
.quad x86_64_start_kernel
ENTRY(initial_gs)
+#ifdef CONFIG_SMP
+ .quad __per_cpu_load
+#else
.quad _boot_cpu_pda
+#endif
__FINITDATA
ENTRY(stack_start)
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index bd47bbd..24d3e0d 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -14,6 +14,7 @@
#include <asm/mpspec.h>
#include <asm/apicdef.h>
#include <asm/highmem.h>
+#include <asm/proto.h>
#ifdef CONFIG_DEBUG_PER_CPU_MAPS
# define DBG(x...) printk(KERN_DEBUG x)
@@ -65,6 +66,16 @@ static void __init setup_node_to_cpumask_map(void);
static inline void setup_node_to_cpumask_map(void) { }
#endif
+#ifdef CONFIG_X86_64
+void __cpuinit load_pda_offset(int cpu)
+{
+ /* Memory clobbers used to order pda/percpu accesses */
+ mb();
+ wrmsrl(MSR_GS_BASE, cpu_pda(cpu));
+ mb();
+}
+#endif
+
#ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
/*
* Copy data used in early init routines from the initial arrays to the
@@ -101,42 +112,6 @@ static void __init setup_per_cpu_maps(void)
*/
unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
EXPORT_SYMBOL(__per_cpu_offset);
-static inline void setup_cpu_pda_map(void) { }
-
-#elif !defined(CONFIG_SMP)
-static inline void setup_cpu_pda_map(void) { }
-
-#else /* CONFIG_SMP && CONFIG_X86_64 */
-
-/*
- * Allocate cpu_pda pointer table and array via alloc_bootmem.
- */
-static void __init setup_cpu_pda_map(void)
-{
- char *pda;
- unsigned long size;
- int cpu;
-
- size = roundup(sizeof(struct x8664_pda), cache_line_size());
-
- /* allocate cpu_pda array and pointer table */
- {
- unsigned long asize = size * (nr_cpu_ids - 1);
-
- pda = alloc_bootmem(asize);
- }
-
- /* initialize pointer table to static pda's */
- for_each_possible_cpu(cpu) {
- if (cpu == 0) {
- /* leave boot cpu pda in place */
- continue;
- }
- cpu_pda(cpu) = (struct x8664_pda *)pda;
- cpu_pda(cpu)->in_bootmem = 1;
- pda += size;
- }
-}
#endif
/*
@@ -151,9 +126,6 @@ void __init setup_per_cpu_areas(void)
int cpu;
unsigned long align = 1;
- /* Setup cpu_pda map */
- setup_cpu_pda_map();
-
/* Copy section for each CPU (we discard the original) */
old_size = PERCPU_ENOUGH_ROOM;
align = max_t(unsigned long, PAGE_SIZE, align);
@@ -185,8 +157,21 @@ void __init setup_per_cpu_areas(void)
cpu, node, __pa(ptr));
}
#endif
- per_cpu_offset(cpu) = ptr - __per_cpu_start;
+
memcpy(ptr, __per_cpu_load, __per_cpu_end - __per_cpu_start);
+#ifdef CONFIG_X86_64
+ cpu_pda(cpu) = (void *)ptr;
+
+ /*
+ * CPU0 modified pda in the init data area, reload pda
+ * offset for CPU0 and clear the area for others.
+ */
+ if (cpu == 0)
+ load_pda_offset(0);
+ else
+ memset(cpu_pda(cpu), 0, sizeof(*cpu_pda(cpu)));
+#endif
+ per_cpu_offset(cpu) = ptr - __per_cpu_start;
DBG("PERCPU: cpu %4d %p\n", cpu, ptr);
}
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 7cd97d9..3a0fec6 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -750,52 +750,6 @@ static void __cpuinit do_fork_idle(struct work_struct *work)
complete(&c_idle->done);
}
-#ifdef CONFIG_X86_64
-
-/* __ref because it's safe to call free_bootmem when after_bootmem == 0. */
-static void __ref free_bootmem_pda(struct x8664_pda *oldpda)
-{
- if (!after_bootmem)
- free_bootmem((unsigned long)oldpda, sizeof(*oldpda));
-}
-
-/*
- * Allocate node local memory for the AP pda.
- *
- * Must be called after the _cpu_pda pointer table is initialized.
- */
-int __cpuinit get_local_pda(int cpu)
-{
- struct x8664_pda *oldpda, *newpda;
- unsigned long size = sizeof(struct x8664_pda);
- int node = cpu_to_node(cpu);
-
- if (cpu_pda(cpu) && !cpu_pda(cpu)->in_bootmem)
- return 0;
-
- oldpda = cpu_pda(cpu);
- newpda = kmalloc_node(size, GFP_ATOMIC, node);
- if (!newpda) {
- printk(KERN_ERR "Could not allocate node local PDA "
- "for CPU %d on node %d\n", cpu, node);
-
- if (oldpda)
- return 0; /* have a usable pda */
- else
- return -1;
- }
-
- if (oldpda) {
- memcpy(newpda, oldpda, size);
- free_bootmem_pda(oldpda);
- }
-
- newpda->in_bootmem = 0;
- cpu_pda(cpu) = newpda;
- return 0;
-}
-#endif /* CONFIG_X86_64 */
-
static int __cpuinit do_boot_cpu(int apicid, int cpu)
/*
* NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
@@ -813,16 +767,6 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu)
};
INIT_WORK(&c_idle.work, do_fork_idle);
-#ifdef CONFIG_X86_64
- /* Allocate node local memory for AP pdas */
- if (cpu > 0) {
- boot_error = get_local_pda(cpu);
- if (boot_error)
- goto restore_state;
- /* if can't get pda memory, can't start cpu */
- }
-#endif
-
alternatives_smp_switch(1);
c_idle.idle = get_idle_for_cpu(cpu);
@@ -937,9 +881,7 @@ do_rest:
inquire_remote_apic(apicid);
}
}
-#ifdef CONFIG_X86_64
-restore_state:
-#endif
+
if (boot_error) {
/* Try to put things back the way they were before ... */
numa_remove_cpu(cpu); /* was set by numa_add_cpu */
diff --git a/arch/x86/kernel/vmlinux_64.lds.S b/arch/x86/kernel/vmlinux_64.lds.S
index f50280d..962f21f 100644
--- a/arch/x86/kernel/vmlinux_64.lds.S
+++ b/arch/x86/kernel/vmlinux_64.lds.S
@@ -5,6 +5,7 @@
#define LOAD_OFFSET __START_KERNEL_map
#include <asm-generic/vmlinux.lds.h>
+#include <asm/asm-offsets.h>
#include <asm/page.h>
#undef i386 /* in case the preprocessor is a 32bit one */
@@ -215,10 +216,11 @@ SECTIONS
/*
* percpu offsets are zero-based on SMP. PERCPU_VADDR() changes the
* output PHDR, so the next output section - __data_nosave - should
- * switch it back to data.init.
+ * switch it back to data.init. Also, pda should be at the head of
+ * percpu area. Preallocate it.
*/
. = ALIGN(PAGE_SIZE);
- PERCPU_VADDR(0, :percpu)
+ PERCPU_VADDR_PREALLOC(0, :percpu, pda_size)
#else
PERCPU(PAGE_SIZE)
#endif
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index acd9b67..ae22284 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -280,16 +280,6 @@ static int __cpuinit xen_cpu_up(unsigned int cpu)
struct task_struct *idle = idle_task(cpu);
int rc;
-#ifdef CONFIG_X86_64
- /* Allocate node local memory for AP pdas */
- WARN_ON(cpu == 0);
- if (cpu > 0) {
- rc = get_local_pda(cpu);
- if (rc)
- return rc;
- }
-#endif
-
#ifdef CONFIG_X86_32
init_gdt(cpu);
per_cpu(current_task, cpu) = idle;
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index fc2f55f..e53319c 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -441,9 +441,10 @@
. = __per_cpu_load + SIZEOF(.data.percpu);
/**
- * PERCPU_VADDR - define output section for percpu area
+ * PERCPU_VADDR_PREALLOC - define output section for percpu area with prealloc
* @vaddr: explicit base address (optional)
* @phdr: destination PHDR (optional)
+ * @prealloc: the size of prealloc area
*
* Macro which expands to output section for percpu area. If @vaddr
* is not blank, it specifies explicit base address and all percpu
@@ -455,11 +456,33 @@
* section in the linker script will go there too. @phdr should have
* a leading colon.
*
+ * If @prealloc is non-zero, the specified number of bytes will be
+ * reserved at the start of percpu area. As the prealloc area is
+ * likely to break alignment, this macro puts areas in increasing
+ * alignment order.
+ *
* This macro defines three symbols, __per_cpu_load, __per_cpu_start
* and __per_cpu_end. The first one is the vaddr of loaded percpu
* init data. __per_cpu_start equals @vaddr and __per_cpu_end is the
* end offset.
*/
+#define PERCPU_VADDR_PREALLOC(vaddr, segment, prealloc) \
+ PERCPU_PROLOG(vaddr) \
+ . += prealloc; \
+ *(.data.percpu) \
+ *(.data.percpu.shared_aligned) \
+ *(.data.percpu.page_aligned) \
+ PERCPU_EPILOG(segment)
+
+/**
+ * PERCPU_VADDR - define output section for percpu area
+ * @vaddr: explicit base address (optional)
+ * @phdr: destination PHDR (optional)
+ *
+ * Macro which expands to output section for percpu area. Mostly
+ * identical to PERCPU_VADDR_PREALLOC(@vaddr, @phdr, 0) other than
+ * using slighly different layout.
+ */
#define PERCPU_VADDR(vaddr, phdr) \
PERCPU_PROLOG(vaddr) \
*(.data.percpu.page_aligned) \
--
1.5.6
--
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