[PATCH] paravirt: header and stubs for paravirtualisation

Create a paravirt.h header for all the critical operations which need to be
replaced with hypervisor calls, and include that instead of defining native
operations, when CONFIG_PARAVIRT.

This patch does the dumbest possible replacement of paravirtualized
instructions: calls through a "paravirt_ops" structure.  Currently these are
function implementations of native hardware: hypervisors will override the ops
structure with their own variants.

All the pv-ops functions are declared "fastcall" so that a specific
register-based ABI is used, to make inlining assember easier.

And:

+From: Andy Whitcroft <apw@shadowen.org>

The paravirt ops introduce a 'weak' attribute onto memory_setup().
Code ordering leads to the following warnings on x86:

    arch/i386/kernel/setup.c:651: warning: weak declaration of
                `memory_setup' after first use results in unspecified behavior

Move memory_setup() to avoid this.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andy Whitcroft <apw@shadowen.org>

11 files changed, 479 insertions, 23 deletions

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index 1f0f7b60995e..bb1fa061c6cf 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -182,6 +182,17 @@ config X86_ES7000
 
 endchoice
 
+config PARAVIRT
+	bool "Paravirtualization support (EXPERIMENTAL)"
+	depends on EXPERIMENTAL
+	help
+	  Paravirtualization is a way of running multiple instances of
+	  Linux on the same machine, under a hypervisor.  This option
+	  changes the kernel so it can modify itself when it is run
+	  under a hypervisor, improving performance significantly.
+	  However, when run without a hypervisor the kernel is
+	  theoretically slower.  If in doubt, say N.
+
 config ACPI_SRAT
 	bool
 	default y
diff --git a/arch/i386/boot/compressed/misc.c b/arch/i386/boot/compressed/misc.c
index dc1538931555..c6798c75c67d 100644
--- a/arch/i386/boot/compressed/misc.c
+++ b/arch/i386/boot/compressed/misc.c
@@ -9,6 +9,7 @@
  * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
  */
 
+#undef CONFIG_PARAVIRT
 #include <linux/linkage.h>
 #include <linux/vmalloc.h>
 #include <linux/screen_info.h>
diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile
index f614854bd71f..406612136049 100644
--- a/arch/i386/kernel/Makefile
+++ b/arch/i386/kernel/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_VM86)		+= vm86.o
 obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
 obj-$(CONFIG_HPET_TIMER) 	+= hpet.o
 obj-$(CONFIG_K8_NB)		+= k8.o
+obj-$(CONFIG_PARAVIRT)		+= paravirt.o
 
 EXTRA_AFLAGS   := -traditional
 
diff --git a/arch/i386/kernel/asm-offsets.c b/arch/i386/kernel/asm-offsets.c
index 0666eb0ed7bc..1b2f3cd33270 100644
--- a/arch/i386/kernel/asm-offsets.c
+++ b/arch/i386/kernel/asm-offsets.c
@@ -101,4 +101,14 @@ void foo(void)
 	BLANK();
  	OFFSET(PDA_cpu, i386_pda, cpu_number);
 	OFFSET(PDA_pcurrent, i386_pda, pcurrent);
+
+#ifdef CONFIG_PARAVIRT
+	BLANK();
+	OFFSET(PARAVIRT_enabled, paravirt_ops, paravirt_enabled);
+	OFFSET(PARAVIRT_irq_disable, paravirt_ops, irq_disable);
+	OFFSET(PARAVIRT_irq_enable, paravirt_ops, irq_enable);
+	OFFSET(PARAVIRT_irq_enable_sysexit, paravirt_ops, irq_enable_sysexit);
+	OFFSET(PARAVIRT_iret, paravirt_ops, iret);
+	OFFSET(PARAVIRT_read_cr0, paravirt_ops, read_cr0);
+#endif
 }
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 0220bc8cbb43..d274612e05cd 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -62,13 +62,6 @@ DF_MASK		= 0x00000400
 NT_MASK		= 0x00004000
 VM_MASK		= 0x00020000
 
-/* These are replaces for paravirtualization */
-#define DISABLE_INTERRUPTS		cli
-#define ENABLE_INTERRUPTS		sti
-#define ENABLE_INTERRUPTS_SYSEXIT	sti; sysexit
-#define INTERRUPT_RETURN		iret
-#define GET_CR0_INTO_EAX		movl %cr0, %eax
-
 #ifdef CONFIG_PREEMPT
 #define preempt_stop		DISABLE_INTERRUPTS; TRACE_IRQS_OFF
 #else
@@ -416,6 +409,20 @@ ldt_ss:
 	jnz restore_nocheck
 	testl $0x00400000, %eax		# returning to 32bit stack?
 	jnz restore_nocheck		# allright, normal return
+
+#ifdef CONFIG_PARAVIRT
+	/*
+	 * The kernel can't run on a non-flat stack if paravirt mode
+	 * is active.  Rather than try to fixup the high bits of
+	 * ESP, bypass this code entirely.  This may break DOSemu
+	 * and/or Wine support in a paravirt VM, although the option
+	 * is still available to implement the setting of the high
+	 * 16-bits in the INTERRUPT_RETURN paravirt-op.
+	 */
+	cmpl $0, paravirt_ops+PARAVIRT_enabled
+	jne restore_nocheck
+#endif
+
 	/* If returning to userspace with 16bit stack,
 	 * try to fix the higher word of ESP, as the CPU
 	 * won't restore it.
@@ -833,6 +840,19 @@ nmi_espfix_stack:
 .previous
 KPROBE_END(nmi)
 
+#ifdef CONFIG_PARAVIRT
+ENTRY(native_iret)
+1:	iret
+.section __ex_table,"a"
+	.align 4
+	.long 1b,iret_exc
+.previous
+
+ENTRY(native_irq_enable_sysexit)
+	sti
+	sysexit
+#endif
+
 KPROBE_ENTRY(int3)
 	RING0_INT_FRAME
 	pushl $-1			# mark this as an int
diff --git a/arch/i386/kernel/i8259.c b/arch/i386/kernel/i8259.c
index 62996cd17084..c8d45821c788 100644
--- a/arch/i386/kernel/i8259.c
+++ b/arch/i386/kernel/i8259.c
@@ -381,7 +381,10 @@ void __init init_ISA_irqs (void)
 	}
 }
 
-void __init init_IRQ(void)
+/* Overridden in paravirt.c */
+void init_IRQ(void) __attribute__((weak, alias("native_init_IRQ")));
+
+void __init native_init_IRQ(void)
 {
 	int i;
 
diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
new file mode 100644
index 000000000000..478192cd4b90
--- /dev/null
+++ b/arch/i386/kernel/paravirt.c
@@ -0,0 +1,404 @@
+/*  Paravirtualization interfaces
+    Copyright (C) 2006 Rusty Russell IBM Corporation
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/efi.h>
+#include <linux/bcd.h>
+
+#include <asm/bug.h>
+#include <asm/paravirt.h>
+#include <asm/desc.h>
+#include <asm/setup.h>
+#include <asm/arch_hooks.h>
+#include <asm/time.h>
+#include <asm/irq.h>
+#include <asm/delay.h>
+
+/* nop stub */
+static void native_nop(void)
+{
+}
+
+static void __init default_banner(void)
+{
+	printk(KERN_INFO "Booting paravirtualized kernel on %s\n",
+	       paravirt_ops.name);
+}
+
+char *memory_setup(void)
+{
+	return paravirt_ops.memory_setup();
+}
+
+static fastcall unsigned long native_get_debugreg(int regno)
+{
+	unsigned long val = 0; 	/* Damn you, gcc! */
+
+	switch (regno) {
+	case 0:
+		asm("movl %%db0, %0" :"=r" (val)); break;
+	case 1:
+		asm("movl %%db1, %0" :"=r" (val)); break;
+	case 2:
+		asm("movl %%db2, %0" :"=r" (val)); break;
+	case 3:
+		asm("movl %%db3, %0" :"=r" (val)); break;
+	case 6:
+		asm("movl %%db6, %0" :"=r" (val)); break;
+	case 7:
+		asm("movl %%db7, %0" :"=r" (val)); break;
+	default:
+		BUG();
+	}
+	return val;
+}
+
+static fastcall void native_set_debugreg(int regno, unsigned long value)
+{
+	switch (regno) {
+	case 0:
+		asm("movl %0,%%db0"	: /* no output */ :"r" (value));
+		break;
+	case 1:
+		asm("movl %0,%%db1"	: /* no output */ :"r" (value));
+		break;
+	case 2:
+		asm("movl %0,%%db2"	: /* no output */ :"r" (value));
+		break;
+	case 3:
+		asm("movl %0,%%db3"	: /* no output */ :"r" (value));
+		break;
+	case 6:
+		asm("movl %0,%%db6"	: /* no output */ :"r" (value));
+		break;
+	case 7:
+		asm("movl %0,%%db7"	: /* no output */ :"r" (value));
+		break;
+	default:
+		BUG();
+	}
+}
+
+void init_IRQ(void)
+{
+	paravirt_ops.init_IRQ();
+}
+
+static fastcall void native_clts(void)
+{
+	asm volatile ("clts");
+}
+
+static fastcall unsigned long native_read_cr0(void)
+{
+	unsigned long val;
+	asm volatile("movl %%cr0,%0\n\t" :"=r" (val));
+	return val;
+}
+
+static fastcall void native_write_cr0(unsigned long val)
+{
+	asm volatile("movl %0,%%cr0": :"r" (val));
+}
+
+static fastcall unsigned long native_read_cr2(void)
+{
+	unsigned long val;
+	asm volatile("movl %%cr2,%0\n\t" :"=r" (val));
+	return val;
+}
+
+static fastcall void native_write_cr2(unsigned long val)
+{
+	asm volatile("movl %0,%%cr2": :"r" (val));
+}
+
+static fastcall unsigned long native_read_cr3(void)
+{
+	unsigned long val;
+	asm volatile("movl %%cr3,%0\n\t" :"=r" (val));
+	return val;
+}
+
+static fastcall void native_write_cr3(unsigned long val)
+{
+	asm volatile("movl %0,%%cr3": :"r" (val));
+}
+
+static fastcall unsigned long native_read_cr4(void)
+{
+	unsigned long val;
+	asm volatile("movl %%cr4,%0\n\t" :"=r" (val));
+	return val;
+}
+
+static fastcall unsigned long native_read_cr4_safe(void)
+{
+	unsigned long val;
+	/* This could fault if %cr4 does not exist */
+	asm("1: movl %%cr4, %0		\n"
+		"2:				\n"
+		".section __ex_table,\"a\"	\n"
+		".long 1b,2b			\n"
+		".previous			\n"
+		: "=r" (val): "0" (0));
+	return val;
+}
+
+static fastcall void native_write_cr4(unsigned long val)
+{
+	asm volatile("movl %0,%%cr4": :"r" (val));
+}
+
+static fastcall unsigned long native_save_fl(void)
+{
+	unsigned long f;
+	asm volatile("pushfl ; popl %0":"=g" (f): /* no input */);
+	return f;
+}
+
+static fastcall void native_restore_fl(unsigned long f)
+{
+	asm volatile("pushl %0 ; popfl": /* no output */
+			     :"g" (f)
+			     :"memory", "cc");
+}
+
+static fastcall void native_irq_disable(void)
+{
+	asm volatile("cli": : :"memory");
+}
+
+static fastcall void native_irq_enable(void)
+{
+	asm volatile("sti": : :"memory");
+}
+
+static fastcall void native_safe_halt(void)
+{
+	asm volatile("sti; hlt": : :"memory");
+}
+
+static fastcall void native_halt(void)
+{
+	asm volatile("hlt": : :"memory");
+}
+
+static fastcall void native_wbinvd(void)
+{
+	asm volatile("wbinvd": : :"memory");
+}
+
+static fastcall unsigned long long native_read_msr(unsigned int msr, int *err)
+{
+	unsigned long long val;
+
+	asm volatile("2: rdmsr ; xorl %0,%0\n"
+		     "1:\n\t"
+		     ".section .fixup,\"ax\"\n\t"
+		     "3:  movl %3,%0 ; jmp 1b\n\t"
+		     ".previous\n\t"
+ 		     ".section __ex_table,\"a\"\n"
+		     "   .align 4\n\t"
+		     "   .long 	2b,3b\n\t"
+		     ".previous"
+		     : "=r" (*err), "=A" (val)
+		     : "c" (msr), "i" (-EFAULT));
+
+	return val;
+}
+
+static fastcall int native_write_msr(unsigned int msr, unsigned long long val)
+{
+	int err;
+	asm volatile("2: wrmsr ; xorl %0,%0\n"
+		     "1:\n\t"
+		     ".section .fixup,\"ax\"\n\t"
+		     "3:  movl %4,%0 ; jmp 1b\n\t"
+		     ".previous\n\t"
+ 		     ".section __ex_table,\"a\"\n"
+		     "   .align 4\n\t"
+		     "   .long 	2b,3b\n\t"
+		     ".previous"
+		     : "=a" (err)
+		     : "c" (msr), "0" ((u32)val), "d" ((u32)(val>>32)),
+		       "i" (-EFAULT));
+	return err;
+}
+
+static fastcall unsigned long long native_read_tsc(void)
+{
+	unsigned long long val;
+	asm volatile("rdtsc" : "=A" (val));
+	return val;
+}
+
+static fastcall unsigned long long native_read_pmc(void)
+{
+	unsigned long long val;
+	asm volatile("rdpmc" : "=A" (val));
+	return val;
+}
+
+static fastcall void native_load_tr_desc(void)
+{
+	asm volatile("ltr %w0"::"q" (GDT_ENTRY_TSS*8));
+}
+
+static fastcall void native_load_gdt(const struct Xgt_desc_struct *dtr)
+{
+	asm volatile("lgdt %0"::"m" (*dtr));
+}
+
+static fastcall void native_load_idt(const struct Xgt_desc_struct *dtr)
+{
+	asm volatile("lidt %0"::"m" (*dtr));
+}
+
+static fastcall void native_store_gdt(struct Xgt_desc_struct *dtr)
+{
+	asm ("sgdt %0":"=m" (*dtr));
+}
+
+static fastcall void native_store_idt(struct Xgt_desc_struct *dtr)
+{
+	asm ("sidt %0":"=m" (*dtr));
+}
+
+static fastcall unsigned long native_store_tr(void)
+{
+	unsigned long tr;
+	asm ("str %0":"=r" (tr));
+	return tr;
+}
+
+static fastcall void native_load_tls(struct thread_struct *t, unsigned int cpu)
+{
+#define C(i) get_cpu_gdt_table(cpu)[GDT_ENTRY_TLS_MIN + i] = t->tls_array[i]
+	C(0); C(1); C(2);
+#undef C
+}
+
+static inline void native_write_dt_entry(void *dt, int entry, u32 entry_low, u32 entry_high)
+{
+	u32 *lp = (u32 *)((char *)dt + entry*8);
+	lp[0] = entry_low;
+	lp[1] = entry_high;
+}
+
+static fastcall void native_write_ldt_entry(void *dt, int entrynum, u32 low, u32 high)
+{
+	native_write_dt_entry(dt, entrynum, low, high);
+}
+
+static fastcall void native_write_gdt_entry(void *dt, int entrynum, u32 low, u32 high)
+{
+	native_write_dt_entry(dt, entrynum, low, high);
+}
+
+static fastcall void native_write_idt_entry(void *dt, int entrynum, u32 low, u32 high)
+{
+	native_write_dt_entry(dt, entrynum, low, high);
+}
+
+static fastcall void native_load_esp0(struct tss_struct *tss,
+				      struct thread_struct *thread)
+{
+	tss->esp0 = thread->esp0;
+
+	/* This can only happen when SEP is enabled, no need to test "SEP"arately */
+	if (unlikely(tss->ss1 != thread->sysenter_cs)) {
+		tss->ss1 = thread->sysenter_cs;
+		wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
+	}
+}
+
+static fastcall void native_io_delay(void)
+{
+	asm volatile("outb %al,$0x80");
+}
+
+/* These are in entry.S */
+extern fastcall void native_iret(void);
+extern fastcall void native_irq_enable_sysexit(void);
+
+static int __init print_banner(void)
+{
+	paravirt_ops.banner();
+	return 0;
+}
+core_initcall(print_banner);
+
+struct paravirt_ops paravirt_ops = {
+	.name = "bare hardware",
+	.paravirt_enabled = 0,
+	.kernel_rpl = 0,
+
+	.banner = default_banner,
+	.arch_setup = native_nop,
+	.memory_setup = machine_specific_memory_setup,
+	.get_wallclock = native_get_wallclock,
+	.set_wallclock = native_set_wallclock,
+	.time_init = time_init_hook,
+	.init_IRQ = native_init_IRQ,
+
+	.cpuid = native_cpuid,
+	.get_debugreg = native_get_debugreg,
+	.set_debugreg = native_set_debugreg,
+	.clts = native_clts,
+	.read_cr0 = native_read_cr0,
+	.write_cr0 = native_write_cr0,
+	.read_cr2 = native_read_cr2,
+	.write_cr2 = native_write_cr2,
+	.read_cr3 = native_read_cr3,
+	.write_cr3 = native_write_cr3,
+	.read_cr4 = native_read_cr4,
+	.read_cr4_safe = native_read_cr4_safe,
+	.write_cr4 = native_write_cr4,
+	.save_fl = native_save_fl,
+	.restore_fl = native_restore_fl,
+	.irq_disable = native_irq_disable,
+	.irq_enable = native_irq_enable,
+	.safe_halt = native_safe_halt,
+	.halt = native_halt,
+	.wbinvd = native_wbinvd,
+	.read_msr = native_read_msr,
+	.write_msr = native_write_msr,
+	.read_tsc = native_read_tsc,
+	.read_pmc = native_read_pmc,
+	.load_tr_desc = native_load_tr_desc,
+	.set_ldt = native_set_ldt,
+	.load_gdt = native_load_gdt,
+	.load_idt = native_load_idt,
+	.store_gdt = native_store_gdt,
+	.store_idt = native_store_idt,
+	.store_tr = native_store_tr,
+	.load_tls = native_load_tls,
+	.write_ldt_entry = native_write_ldt_entry,
+	.write_gdt_entry = native_write_gdt_entry,
+	.write_idt_entry = native_write_idt_entry,
+	.load_esp0 = native_load_esp0,
+
+	.set_iopl_mask = native_set_iopl_mask,
+	.io_delay = native_io_delay,
+	.const_udelay = __const_udelay,
+
+	.irq_enable_sysexit = native_irq_enable_sysexit,
+	.iret = native_iret,
+};
+EXPORT_SYMBOL(paravirt_ops);
diff --git a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
index e5bb87aa5a45..695d53fd14de 100644
--- a/arch/i386/kernel/setup.c
+++ b/arch/i386/kernel/setup.c
@@ -495,6 +495,12 @@ static void set_mca_bus(int x)
 static void set_mca_bus(int x) { }
 #endif
 
+/* Overridden in paravirt.c if CONFIG_PARAVIRT */
+char * __attribute__((weak)) memory_setup(void)
+{
+	return machine_specific_memory_setup();
+}
+
 /*
  * Determine if we were loaded by an EFI loader.  If so, then we have also been
  * passed the efi memmap, systab, etc., so we should use these data structures
@@ -547,7 +553,7 @@ void __init setup_arch(char **cmdline_p)
 		efi_init();
 	else {
 		printk(KERN_INFO "BIOS-provided physical RAM map:\n");
-		print_memory_map(machine_specific_memory_setup());
+		print_memory_map(memory_setup());
 	}
 
 	copy_edd();
diff --git a/arch/i386/kernel/smpboot.c b/arch/i386/kernel/smpboot.c
index 095636620fa2..cd7de9c9654b 100644
--- a/arch/i386/kernel/smpboot.c
+++ b/arch/i386/kernel/smpboot.c
@@ -33,6 +33,11 @@
  *		Dave Jones	:	Report invalid combinations of Athlon CPUs.
 *		Rusty Russell	:	Hacked into shape for new "hotplug" boot process. */
 
+
+/* SMP boot always wants to use real time delay to allow sufficient time for
+ * the APs to come online */
+#define USE_REAL_TIME_DELAY
+
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
diff --git a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
index 78af572fd17c..c505b16c0990 100644
--- a/arch/i386/kernel/time.c
+++ b/arch/i386/kernel/time.c
@@ -56,6 +56,7 @@
 #include <asm/uaccess.h>
 #include <asm/processor.h>
 #include <asm/timer.h>
+#include <asm/time.h>
 
 #include "mach_time.h"
 
@@ -116,10 +117,7 @@ static int set_rtc_mmss(unsigned long nowtime)
 	/* gets recalled with irq locally disabled */
 	/* XXX - does irqsave resolve this? -johnstul */
 	spin_lock_irqsave(&rtc_lock, flags);
-	if (efi_enabled)
-		retval = efi_set_rtc_mmss(nowtime);
-	else
-		retval = mach_set_rtc_mmss(nowtime);
+	retval = set_wallclock(nowtime);
 	spin_unlock_irqrestore(&rtc_lock, flags);
 
 	return retval;
@@ -223,10 +221,7 @@ unsigned long get_cmos_time(void)
 
 	spin_lock_irqsave(&rtc_lock, flags);
 
-	if (efi_enabled)
-		retval = efi_get_time();
-	else
-		retval = mach_get_cmos_time();
+	retval = get_wallclock();
 
 	spin_unlock_irqrestore(&rtc_lock, flags);
 
@@ -370,7 +365,7 @@ static void __init hpet_time_init(void)
 		printk("Using HPET for base-timer\n");
 	}
 
-	time_init_hook();
+	do_time_init();
 }
 #endif
 
@@ -392,5 +387,5 @@ void __init time_init(void)
 
 	do_settimeofday(&ts);
 
-	time_init_hook();
+	do_time_init();
 }
diff --git a/arch/i386/power/cpu.c b/arch/i386/power/cpu.c
index 5a1abeff033b..2c15500f8713 100644
--- a/arch/i386/power/cpu.c
+++ b/arch/i386/power/cpu.c
@@ -26,8 +26,8 @@ void __save_processor_state(struct saved_context *ctxt)
 	/*
 	 * descriptor tables
 	 */
- 	store_gdt(&ctxt->gdt_limit);
- 	store_idt(&ctxt->idt_limit);
+ 	store_gdt(&ctxt->gdt);
+ 	store_idt(&ctxt->idt);
  	store_tr(ctxt->tr);
 
 	/*
@@ -99,8 +99,8 @@ void __restore_processor_state(struct saved_context *ctxt)
 	 * now restore the descriptor tables to their proper values
 	 * ltr is done i fix_processor_context().
 	 */
- 	load_gdt(&ctxt->gdt_limit);
- 	load_idt(&ctxt->idt_limit);
+ 	load_gdt(&ctxt->gdt);
+ 	load_idt(&ctxt->idt);
 
 	/*
 	 * segment registers