[PATCH] i386: Page-align the GDT

Xen wants a dedicated page for the GDT.  I believe VMI likes it too.
lguest, KVM and native don't care.

Simple transformation to page-aligned "struct gdt_page".

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Acked-by: Jeremy Fitzhardinge <jeremy@xensource.com>

5 files changed, 13 insertions, 8 deletions

diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c
index 58128585ae60..7a4c036d93c8 100644
--- a/arch/i386/kernel/cpu/common.c
+++ b/arch/i386/kernel/cpu/common.c
@@ -22,7 +22,7 @@
 
 #include "cpu.h"
 
-DEFINE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]) = {
+DEFINE_PER_CPU(struct gdt_page, gdt_page) = { .gdt = {
         [GDT_ENTRY_KERNEL_CS] = { 0x0000ffff, 0x00cf9a00 },
         [GDT_ENTRY_KERNEL_DS] = { 0x0000ffff, 0x00cf9200 },
         [GDT_ENTRY_DEFAULT_USER_CS] = { 0x0000ffff, 0x00cffa00 },
@@ -48,8 +48,8 @@ DEFINE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]) = {
 
         [GDT_ENTRY_ESPFIX_SS] = { 0x00000000, 0x00c09200 },
         [GDT_ENTRY_PDA] = { 0x00000000, 0x00c09200 }, /* set in setup_pda */
-};
-EXPORT_PER_CPU_SYMBOL_GPL(cpu_gdt);
+} };
+EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);
 
 DEFINE_PER_CPU(struct i386_pda, _cpu_pda);
 EXPORT_PER_CPU_SYMBOL(_cpu_pda);
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index e07473c0d3e7..3e4aa1fd33e2 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -557,7 +557,7 @@ END(syscall_badsys)
 #define FIXUP_ESPFIX_STACK \
         /* since we are on a wrong stack, we cant make it a C code :( */ \
         movl %fs:PDA_cpu, %ebx; \
-        PER_CPU(cpu_gdt, %ebx); \
+        PER_CPU(gdt_page, %ebx); \
         GET_DESC_BASE(GDT_ENTRY_ESPFIX_SS, %ebx, %eax, %ax, %al, %ah); \
         addl %esp, %eax; \
         pushl $__KERNEL_DS; \
diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index cc46494787e8..bb36c24311b4 100644
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -598,7 +598,7 @@ idt_descr:
         .word 0                         # 32 bit align gdt_desc.address
 ENTRY(early_gdt_descr)
         .word GDT_ENTRIES*8-1
-        .long per_cpu__cpu_gdt          /* Overwritten for secondary CPUs */
+        .long per_cpu__gdt_page         /* Overwritten for secondary CPUs */
 
 /*
  * The boot_gdt must mirror the equivalent in setup.S and is
diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index e0a23bee6967..f21b41e7770c 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -1030,7 +1030,7 @@ fastcall void do_spurious_interrupt_bug(struct pt_regs * regs,
 fastcall unsigned long patch_espfix_desc(unsigned long uesp,
                                           unsigned long kesp)
 {
-        struct desc_struct *gdt = __get_cpu_var(cpu_gdt);
+        struct desc_struct *gdt = __get_cpu_var(gdt_page).gdt;
         unsigned long base = (kesp - uesp) & -THREAD_SIZE;
         unsigned long new_kesp = kesp - base;
         unsigned long lim_pages = (new_kesp | (THREAD_SIZE - 1)) >> PAGE_SHIFT;
diff --git a/include/asm-i386/desc.h b/include/asm-i386/desc.h
index 4a974064e928..c547403f341d 100644
--- a/include/asm-i386/desc.h
+++ b/include/asm-i386/desc.h
@@ -18,10 +18,15 @@ struct Xgt_desc_struct {
         unsigned short pad;
 } __attribute__ ((packed));
 
-DECLARE_PER_CPU(struct desc_struct, cpu_gdt[GDT_ENTRIES]);
+struct gdt_page
+{
+        struct desc_struct gdt[GDT_ENTRIES];
+} __attribute__((aligned(PAGE_SIZE)));
+DECLARE_PER_CPU(struct gdt_page, gdt_page);
+
 static inline struct desc_struct *get_cpu_gdt_table(unsigned int cpu)
 {
-        return per_cpu(cpu_gdt, cpu);
+        return per_cpu(gdt_page, cpu).gdt;
 }
 
 extern struct Xgt_desc_struct idt_descr;