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x86 setup: add a near jump to serialize %cr0 on 386/486

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The 386 and 486 needs a jump immediately after setting %cr0 in order
to serialize the pipeline.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin
2007-11-04 17:50:12 -08:00
parent b55d1b1814
commit 7ed192906a
1 changed files with 2 additions and 2 deletions
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4
arch/x86/boot/pmjump.S
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@@ -31,14 +31,14 @@ protected_mode_jump:
xorl %ebx, %ebx # Flag to indicate this is a boot xorl %ebx, %ebx # Flag to indicate this is a boot
movl %edx, %esi # Pointer to boot_params table movl %edx, %esi # Pointer to boot_params table
movl %eax, 2f # Patch ljmpl instruction movl %eax, 2f # Patch ljmpl instruction
jmp 1f # Short jump to flush instruction q.
1:
movw $__BOOT_DS, %cx movw $__BOOT_DS, %cx
movl %cr0, %edx movl %cr0, %edx
orb $1, %dl # Protected mode (PE) bit orb $1, %dl # Protected mode (PE) bit
movl %edx, %cr0 movl %edx, %cr0
jmp 1f # Short jump to serialize on 386/486
1:
movw %cx, %ds movw %cx, %ds
movw %cx, %es movw %cx, %es