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2024-05-10 10ebd8556b7990499c896a550e3d416b444211e6

 kernel/arch/x86/kernel/head64.c
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@@ -20,13 +20,13 @@
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 #include <linux/io.h>
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 #include <linux/memblock.h>
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 #include <linux/mem_encrypt.h>
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+#include <linux/pgtable.h>
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 #include <asm/processor.h>
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 #include <asm/proto.h>
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 #include <asm/smp.h>
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 #include <asm/setup.h>
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 #include <asm/desc.h>
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-#include <asm/pgtable.h>
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 #include <asm/tlbflush.h>
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 #include <asm/sections.h>
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 #include <asm/kdebug.h>
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@@ -36,6 +36,11 @@
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 #include <asm/microcode.h>
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 #include <asm/kasan.h>
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 #include <asm/fixmap.h>
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+#include <asm/realmode.h>
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+#include <asm/desc.h>
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+#include <asm/extable.h>
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+#include <asm/trapnr.h>
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+#include <asm/sev-es.h>
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 /*
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  * Manage page tables very early on.
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@@ -61,7 +66,25 @@
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 EXPORT_SYMBOL(vmemmap_base);
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 #endif
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68
 
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-#define __head	__section(.head.text)
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+/*
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+ * GDT used on the boot CPU before switching to virtual addresses.
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+ */
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+static struct desc_struct startup_gdt[GDT_ENTRIES] = {
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+	[GDT_ENTRY_KERNEL32_CS]         = GDT_ENTRY_INIT(0xc09b, 0, 0xfffff),
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+	[GDT_ENTRY_KERNEL_CS]           = GDT_ENTRY_INIT(0xa09b, 0, 0xfffff),
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+	[GDT_ENTRY_KERNEL_DS]           = GDT_ENTRY_INIT(0xc093, 0, 0xfffff),
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+};
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+
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+/*
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+ * Address needs to be set at runtime because it references the startup_gdt
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+ * while the kernel still uses a direct mapping.
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+ */
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+static struct desc_ptr startup_gdt_descr = {
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+	.size = sizeof(startup_gdt),
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+	.address = 0,
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+};
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+
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+#define __head	__section(".head.text")
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 static void __head *fixup_pointer(void *ptr, unsigned long physaddr)
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 {
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@@ -297,7 +320,7 @@
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 }
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 /* Create a new PMD entry */
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-int __init __early_make_pgtable(unsigned long address, pmdval_t pmd)
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+bool __init __early_make_pgtable(unsigned long address, pmdval_t pmd)
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 {
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 	unsigned long physaddr = address - __PAGE_OFFSET;
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 	pgdval_t pgd, *pgd_p;
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@@ -307,7 +330,7 @@
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 	/* Invalid address or early pgt is done ?  */
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 	if (physaddr >= MAXMEM || read_cr3_pa() != __pa_nodebug(early_top_pgt))
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-		return -1;
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+		return false;
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 again:
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 	pgd_p = &early_top_pgt[pgd_index(address)].pgd;
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@@ -364,10 +387,10 @@
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 	}
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 	pmd_p[pmd_index(address)] = pmd;
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389
 
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-	return 0;
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+	return true;
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 }
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-int __init early_make_pgtable(unsigned long address)
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+static bool __init early_make_pgtable(unsigned long address)
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 {
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 	unsigned long physaddr = address - __PAGE_OFFSET;
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 	pmdval_t pmd;
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@@ -377,12 +400,27 @@
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 	return __early_make_pgtable(address, pmd);
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 }
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+void __init do_early_exception(struct pt_regs *regs, int trapnr)
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+{
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+	if (trapnr == X86_TRAP_PF &&
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+	    early_make_pgtable(native_read_cr2()))
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+		return;
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+
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+	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT) &&
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+	    trapnr == X86_TRAP_VC && handle_vc_boot_ghcb(regs))
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+		return;
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+
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+	early_fixup_exception(regs, trapnr);
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+}
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+
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 /* Don't add a printk in there. printk relies on the PDA which is not initialized 
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    yet. */
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 static void __init clear_bss(void)
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 {
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 	memset(__bss_start, 0,
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 	       (unsigned long) __bss_stop - (unsigned long) __bss_start);
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+	memset(__brk_base, 0,
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+	       (unsigned long) __brk_limit - (unsigned long) __brk_base);
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 }
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 static unsigned long get_cmd_line_ptr(void)
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@@ -405,7 +443,7 @@
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 	 */
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 	sme_map_bootdata(real_mode_data);
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-	memcpy(&boot_params, real_mode_data, sizeof boot_params);
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+	memcpy(&boot_params, real_mode_data, sizeof(boot_params));
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 	sanitize_boot_params(&boot_params);
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 	cmd_line_ptr = get_cmd_line_ptr();
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 	if (cmd_line_ptr) {
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@@ -489,3 +527,81 @@
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 	start_kernel();
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 }
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+
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+/*
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+ * Data structures and code used for IDT setup in head_64.S. The bringup-IDT is
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+ * used until the idt_table takes over. On the boot CPU this happens in
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+ * x86_64_start_kernel(), on secondary CPUs in start_secondary(). In both cases
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+ * this happens in the functions called from head_64.S.
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+ *
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+ * The idt_table can't be used that early because all the code modifying it is
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+ * in idt.c and can be instrumented by tracing or KASAN, which both don't work
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+ * during early CPU bringup. Also the idt_table has the runtime vectors
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+ * configured which require certain CPU state to be setup already (like TSS),
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+ * which also hasn't happened yet in early CPU bringup.
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+ */
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+static gate_desc bringup_idt_table[NUM_EXCEPTION_VECTORS] __page_aligned_data;
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+
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+static struct desc_ptr bringup_idt_descr = {
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+	.size		= (NUM_EXCEPTION_VECTORS * sizeof(gate_desc)) - 1,
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+	.address	= 0, /* Set at runtime */
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+};
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+
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+static void set_bringup_idt_handler(gate_desc *idt, int n, void *handler)
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+{
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+#ifdef CONFIG_AMD_MEM_ENCRYPT
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+	struct idt_data data;
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+	gate_desc desc;
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+
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+	init_idt_data(&data, n, handler);
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+	idt_init_desc(&desc, &data);
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+	native_write_idt_entry(idt, n, &desc);
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+#endif
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+}
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+
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+/* This runs while still in the direct mapping */
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+static void startup_64_load_idt(unsigned long physbase)
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+{
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+	struct desc_ptr *desc = fixup_pointer(&bringup_idt_descr, physbase);
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+	gate_desc *idt = fixup_pointer(bringup_idt_table, physbase);
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+
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+
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+	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
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+		void *handler;
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+
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+		/* VMM Communication Exception */
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+		handler = fixup_pointer(vc_no_ghcb, physbase);
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+		set_bringup_idt_handler(idt, X86_TRAP_VC, handler);
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+	}
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+
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+	desc->address = (unsigned long)idt;
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+	native_load_idt(desc);
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+}
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+
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+/* This is used when running on kernel addresses */
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+void early_setup_idt(void)
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+{
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+	/* VMM Communication Exception */
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+	if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT))
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+		set_bringup_idt_handler(bringup_idt_table, X86_TRAP_VC, vc_boot_ghcb);
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+
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+	bringup_idt_descr.address = (unsigned long)bringup_idt_table;
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+	native_load_idt(&bringup_idt_descr);
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+}
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+
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+/*
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+ * Setup boot CPU state needed before kernel switches to virtual addresses.
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+ */
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+void __head startup_64_setup_env(unsigned long physbase)
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+{
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+	/* Load GDT */
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+	startup_gdt_descr.address = (unsigned long)fixup_pointer(startup_gdt, physbase);
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+	native_load_gdt(&startup_gdt_descr);
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+
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+	/* New GDT is live - reload data segment registers */
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+	asm volatile("movl %%eax, %%ds\n"
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+		     "movl %%eax, %%ss\n"
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+		     "movl %%eax, %%es\n" : : "a"(__KERNEL_DS) : "memory");
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+
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+	startup_64_load_idt(physbase);
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+}