This patch:
[PATCH] x86: GDT alignment fix
completely broke my voyager boot sequence. The reason is that the patch
introduces a subtle dependence on the assumption that the boot CPU is
CPU0, which is untrue for voyager. I think the most correct fix for
this is to use a per_cpu for cpu_gdt_descr and still allocate the actual
descriptors as page allocations. I think it's also much more efficient
to do these allocations in cpu_init() where they'll be automatic for all
subarchitectures, rather than placing them in each do_boot_cpu
implementation. Note, I've also fixed a potentially hard to trace bug
as well: the secondaries in the prior scheme were actually using the
Boot CPU's GDT to come up with ... whatever cpu_init() and subsequent
manipulations alter it to be. This implementation goes back to using
the special (and now not altered) cpu_gdt_table for all booting CPUs.
Signed-off-by: James Bottomley <[email protected]>
---
James
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:
@@ -589,10 +610,10 @@ void __devinit cpu_init(void)
((((__u64)stk16_off) << 32) & 0xff00000000000000ULL) |
(CPU_16BIT_STACK_SIZE - 1);
- cpu_gdt_descr[cpu].size = GDT_SIZE - 1;
- cpu_gdt_descr[cpu].address = (unsigned long)gdt;
+ cpu_gdt_descr->size = GDT_SIZE - 1;
+ cpu_gdt_descr->address = (unsigned long)gdt;
- load_gdt(&cpu_gdt_descr[cpu]);
+ load_gdt(cpu_gdt_descr);
load_idt(&idt_descr);
/*
diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index 870f20b..e437fb3 100644
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -525,5 +525,3 @@ ENTRY(cpu_gdt_table)
.quad 0x0000000000000000 /* 0xf0 - unused */
.quad 0x0000000000000000 /* 0xf8 - GDT entry 31: double-fault TSS */
- /* Be sure this is zeroed to avoid false validations in Xen */
- .fill PAGE_SIZE_asm / 8 - GDT_ENTRIES,8,0
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index b3c2e2c..9ed449a 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -903,12 +903,6 @@ static int __devinit do_boot_cpu(int api
unsigned long start_eip;
unsigned short nmi_high = 0, nmi_low = 0;
- if (!cpu_gdt_descr[cpu].address &&
- !(cpu_gdt_descr[cpu].address = get_zeroed_page(GFP_KERNEL))) {
- printk("Failed to allocate GDT for CPU %d\n", cpu);
- return 1;
- }
-
++cpucount;
/*
diff --git a/include/asm-i386/desc.h b/include/asm-i386/desc.h
index 494e73b..89b9c32 100644
--- a/include/asm-i386/desc.h
+++ b/include/asm-i386/desc.h
@@ -25,10 +25,12 @@ struct Xgt_desc_struct {
} __attribute__ ((packed));
extern struct Xgt_desc_struct idt_descr, cpu_gdt_descr[NR_CPUS];
+DECLARE_PER_CPU(struct Xgt_desc_struct, cpu_gdt_descr);
+
static inline struct desc_struct *get_cpu_gdt_table(unsigned int cpu)
{
- return ((struct desc_struct *)cpu_gdt_descr[cpu].address);
+ return (struct desc_struct *)per_cpu(cpu_gdt_descr, cpu).address;
}
#define load_TR_desc() __asm__ __volatile__("ltr %w0"::"q" (GDT_ENTRY_TSS*8))
-
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