James Bottomley wrote:
This patch:
I'm not adverse to making the gdt descriptors part of the per-cpu data.
But I think your patch is missing some necessary changes to
include/asm-i386/desc.h - what do you plan to do with the following
definition there?
extern struct Xgt_desc_struct idt_descr, cpu_gdt_descr[NR_CPUS];
Also, it seems likely you may have broken APM and/or PnP BIOS.
diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index cbc3206..d561a56 100644
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -4,6 +4,7 @@
#include <linux/smp.h>
#include <linux/module.h>
#include <linux/percpu.h>
+#include <linux/bootmem.h>
#include <asm/semaphore.h>
#include <asm/processor.h>
#include <asm/i387.h>
@@ -18,6 +19,9 @@
#include "cpu.h"
+DEFINE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
+EXPORT_PER_CPU_SYMBOL(cpu_gdt_descr);
+
DEFINE_PER_CPU(unsigned char, cpu_16bit_stack[CPU_16BIT_STACK_SIZE]);
EXPORT_PER_CPU_SYMBOL(cpu_16bit_stack);
@@ -559,8 +563,9 @@ void __devinit cpu_init(void)
int cpu = smp_processor_id();
struct tss_struct * t = &per_cpu(init_tss, cpu);
struct thread_struct *thread = ¤t->thread;
- struct desc_struct *gdt = get_cpu_gdt_table(cpu);
+ struct desc_struct *gdt;
__u32 stk16_off = (__u32)&per_cpu(cpu_16bit_stack, cpu);
+ struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, cpu);
if (cpu_test_and_set(cpu, cpu_initialized)) {
printk(KERN_WARNING "CPU#%d already initialized!\n", cpu);
@@ -577,6 +582,22 @@ void __devinit cpu_init(void)
set_in_cr4(X86_CR4_TSD);
}
+ /* This is a horrible hack to allocate the GDT. The problem
+ * is that cpu_init() is called really early for the boot CPU
+ * (and hence needs bootmem) but much later for the secondary
+ * CPUs, when bootmem will have gone away */
+ if (NODE_DATA(0)->bdata->node_bootmem_map) {
+ gdt = (struct desc_struct *)alloc_bootmem_pages(PAGE_SIZE);
+ /* alloc_bootmem_pages panics on failure, so no check */
+ memset(gdt, 0, PAGE_SIZE);
+ } else {
+ gdt = (struct desc_struct *)get_zeroed_page(GFP_KERNEL);
+ if (unlikely(!gdt)) {
+ printk(KERN_CRIT "CPU%d failed to allocate GDT\n", cpu);
+ for (;;) local_irq_enable();
+ }
+ }
+
/*
* Initialize the per-CPU GDT with the boot GDT,
* and set up the GDT descriptor:
Can't you get rid of this ugly hack _and_ optimize the code at the same
time? I don't understand the details of voyager bringup, but it seems
clear that the BSP or node 0 is special in both sub-architectures. If
it is special anyway, the conditional logic can be merged, and better
yet, the allocation for the first caller of cpu_init() can skip the
allocation entirely - it can simply use the boot GDT, which is already
page-aligned and ready to go. This gets rid of the
alloc_bootmem_pages() piece of the hack above.
Also, it seems you left the allocation of the GDT in do_boot_cpu(). How
do you plan to make sure that GDT allocation is compatible with hotplug
CPU startup? I was worried about that, which is why I moved the GDT
allocation for secondary processors (originally in
arch/i386/kernel/cpu/common.c) to smpboot.c.
Zach
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