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x86 setup: initialize LDTR and TR to make life easier to Intel VT

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Intel VT doesn't like to engage when the protected-mode state isn't
fully initialized.  Make life easier for it by initializing LDTR (to
null) and TR (to a dummy hunk of low memory which will never actually
be touched.)

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
H. Peter Anvin 2008-01-30 13:33:02 +01:00 committed by Ingo Molnar
parent c4d9ba6da9
commit 88089519f3
3 changed files with 14 additions and 0 deletions
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4
arch/x86/boot/pm.c
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@ -121,6 +121,10 @@ static void setup_gdt(void)
[GDT_ENTRY_BOOT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
/* DS: data, read/write, 4 GB, base 0 */
[GDT_ENTRY_BOOT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
/* TSS: 32-bit tss, 104 bytes, base 4096 */
/* We only have a TSS here to keep Intel VT happy;
we don't actually use it for anything. */
[GDT_ENTRY_BOOT_TSS] = GDT_ENTRY(0x0089, 4096, 103),
};
/* Xen HVM incorrectly stores a pointer to the gdt_ptr, instead
of the gdt_ptr contents. Thus, make it static so it will

7
arch/x86/boot/pmjump.S
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@ -36,6 +36,7 @@ protected_mode_jump:
addl %ebx, 2f
movw $__BOOT_DS, %cx
movw $__BOOT_TSS, %di
movl %cr0, %edx
orb $1, %dl # Protected mode (PE) bit
@ -63,6 +64,9 @@ in_pm32:
# a valid stack if some debugging hack wants to use it.
addl %ebx, %esp
# Set up TR to make Intel VT happy
ltr %di
# Clear registers to allow for future extensions to the
# 32-bit boot protocol
xorl %ecx, %ecx
@ -71,6 +75,9 @@ in_pm32:
xorl %ebp, %ebp
xorl %edi, %edi
# Set up LDTR to make Intel VT happy
lldt %cx
jmpl *%eax # Jump to the 32-bit entrypoint
.size in_pm32, .-in_pm32

3
include/asm-x86/segment.h
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@ -9,6 +9,9 @@
#define GDT_ENTRY_BOOT_DS (GDT_ENTRY_BOOT_CS + 1)
#define __BOOT_DS (GDT_ENTRY_BOOT_DS * 8)
#define GDT_ENTRY_BOOT_TSS (GDT_ENTRY_BOOT_CS + 2)
#define __BOOT_TSS (GDT_ENTRY_BOOT_TSS * 8)
#ifdef CONFIG_X86_32
/*
* The layout of the per-CPU GDT under Linux: