Messages in this thread Patch in this message | | | Subject | Re: [PATCH] fix broken x86 SMP boot sequence | From | James Bottomley <> | Date | Wed, 22 Feb 2006 17:49:38 -0600 |
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On Wed, 2006-02-22 at 10:08 -0800, Zachary Amsden wrote: > 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];
Actually, I checked ... it looks like the externel definition of cpu_gdt_descr can be dumped ... nothing's using it (well, at least in a voyager build), so I updated the patch.
James
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diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c index cbc3206..d561a56 100644 Index: BUILD-2.6/arch/i386/kernel/cpu/common.c =================================================================== --- BUILD-2.6.orig/arch/i386/kernel/cpu/common.c 2006-02-22 13:53:43.000000000 -0600 +++ BUILD-2.6/arch/i386/kernel/cpu/common.c 2006-02-22 15:28:37.000000000 -0600 @@ -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); @@ -571,8 +575,9 @@ 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); @@ -589,6 +594,22 @@ 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: @@ -601,10 +622,10 @@ ((((__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); /* Index: BUILD-2.6/arch/i386/kernel/head.S =================================================================== --- BUILD-2.6.orig/arch/i386/kernel/head.S 2006-02-22 13:53:43.000000000 -0600 +++ BUILD-2.6/arch/i386/kernel/head.S 2006-02-22 15:28:37.000000000 -0600 @@ -534,5 +534,3 @@ .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 Index: BUILD-2.6/arch/i386/kernel/smpboot.c =================================================================== --- BUILD-2.6.orig/arch/i386/kernel/smpboot.c 2006-02-22 13:53:43.000000000 -0600 +++ BUILD-2.6/arch/i386/kernel/smpboot.c 2006-02-22 15:28:37.000000000 -0600 @@ -898,12 +898,6 @@ 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; /* Index: BUILD-2.6/include/asm-i386/desc.h =================================================================== --- BUILD-2.6.orig/include/asm-i386/desc.h 2006-02-22 13:53:47.000000000 -0600 +++ BUILD-2.6/include/asm-i386/desc.h 2006-02-22 15:28:37.000000000 -0600 @@ -24,11 +24,13 @@ unsigned short pad; } __attribute__ ((packed)); -extern struct Xgt_desc_struct idt_descr, cpu_gdt_descr[NR_CPUS]; +extern struct Xgt_desc_struct idt_descr; +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)) Index: BUILD-2.6/arch/i386/kernel/i386_ksyms.c =================================================================== --- BUILD-2.6.orig/arch/i386/kernel/i386_ksyms.c 2006-02-22 15:26:57.000000000 -0600 +++ BUILD-2.6/arch/i386/kernel/i386_ksyms.c 2006-02-22 15:28:54.000000000 -0600 @@ -3,8 +3,6 @@ #include <asm/checksum.h> #include <asm/desc.h> -EXPORT_SYMBOL_GPL(cpu_gdt_descr); - EXPORT_SYMBOL(__down_failed); EXPORT_SYMBOL(__down_failed_interruptible); EXPORT_SYMBOL(__down_failed_trylock);
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