Jeremy Fitzhardinge wrote:
>
> Maybe it really does require the far jump immediately after setting PE
> in cr0...
>
> Hm, I don't remember this paragraph being in vol 3a, section 8.9.1
> before. Is it a recent addition?
>
> Random failures can occur if other instructions exist between steps
> 3 and 4 above. Failures will be readily seen in some situations,
> such as when instructions that reference memory are inserted between
> steps 3 and 4 while in system management mode.
>
I don't remember that, either.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Remove old comments that include the old arch/i386 directory.
Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
To set CR0.PE, use the X86_CR0_PE macro defined in
<asm/processor-flags.h> instead of hardcoding it as a constant (1).
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>
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>
Make the transition to protected mode more paranoid by having
back-to-back near jump (to synchronize the 386/486 prefetch queue) and
far jump (to set up the code segment.)
While we're at it, zero as many registers as practical (for future
expandability of the 32-bit entry interface) and enter 32-bit mode
with a valid stack. Note that the 32-bit code cannot rely on this
stack, or we'll break all other existing users of the 32-bit
entrypoint, but it may make debugging hacks easier to write.
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>
In accordance with the newly formalized 32-bit boot protocol, set
%ebx == %ebp == %edi == 0 in order to support future extensions to the
protocol.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This is the code which actually does the switch to protected mode,
including all preparation. It is also responsible for invoking the
boot loader hooks, if present.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
H. Peter Anvin