提交 1a51e3a0 编写于 作者: T Tejun Heo 提交者: Ingo Molnar

x86: fold pda into percpu area on SMP

[ Based on original patch from Christoph Lameter and Mike Travis. ]

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: NTejun Heo <tj@kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
上级 c8f3329a
#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>
......
......@@ -19,8 +19,6 @@
#include <asm/thread_info.h>
#include <asm/cpumask.h>
extern int __cpuinit get_local_pda(int cpu);
extern int smp_num_siblings;
extern unsigned int num_processors;
......
......@@ -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
......
......@@ -893,10 +893,8 @@ 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;
......
......@@ -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;
#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);
......
......@@ -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)
......
......@@ -13,6 +13,7 @@
#include <asm/mpspec.h>
#include <asm/apicdef.h>
#include <asm/highmem.h>
#include <asm/proto.h>
#include <asm/cpumask.h>
#ifdef CONFIG_DEBUG_PER_CPU_MAPS
......@@ -65,6 +66,36 @@ 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 /* CONFIG_SMP && CONFIG_X86_64 */
#ifdef CONFIG_X86_64
/* correctly size the local cpu masks */
static void setup_cpu_local_masks(void)
{
alloc_bootmem_cpumask_var(&cpu_initialized_mask);
alloc_bootmem_cpumask_var(&cpu_callin_mask);
alloc_bootmem_cpumask_var(&cpu_callout_mask);
alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);
}
#else /* CONFIG_X86_32 */
static inline void setup_cpu_local_masks(void)
{
}
#endif /* CONFIG_X86_32 */
#ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
/*
* Copy data used in early init routines from the initial arrays to the
......@@ -101,63 +132,7 @@ 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 /* CONFIG_SMP && CONFIG_X86_64 */
#ifdef CONFIG_X86_64
/* correctly size the local cpu masks */
static void setup_cpu_local_masks(void)
{
alloc_bootmem_cpumask_var(&cpu_initialized_mask);
alloc_bootmem_cpumask_var(&cpu_callin_mask);
alloc_bootmem_cpumask_var(&cpu_callout_mask);
alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);
}
#else /* CONFIG_X86_32 */
static inline void setup_cpu_local_masks(void)
{
}
#endif /* CONFIG_X86_32 */
#endif
/*
* Great future plan:
......@@ -171,9 +146,6 @@ 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);
......@@ -204,8 +176,21 @@ 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);
}
......
......@@ -744,52 +744,6 @@ 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
......@@ -807,16 +761,6 @@ 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);
......@@ -931,9 +875,7 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu)
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 */
......
......@@ -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
......
......@@ -283,16 +283,6 @@ 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;
......
......@@ -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) \
......
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