Re: SMP on the MacBook

[gimli <gimli@dark-green.com>]

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Hi.

I have xen running on my Macbook. The problem is cause by grub.
When i start the xen entry in grub with the key "return" xen
fails too boot. When i use the "Cursor key right" to start
the xen entry xen boots fine. I used the atached patch against
grub 0.97 for the Intel Macs.

cu

Edgar (gimli) Hucek

Marco Gerards schrieb:
> Hi,
> 
> For a while now I have been trying to debug an issue with Xen on the
> MacBook, doing this is part of my Summer of Code project to get Xen
> working properly on the Intel Mac.  In case some of you don't know,
> the MacBook is an Intel Core Duo based laptop from Apple, which lacks
> some legacy hardware.
> 
> Xen (testing) works perfectly for me when starting it with "nosmp",
> however when not using it, it crashes while starting up the second
> core.  There have been some bug report on this issue already.
> 
> Below I will explain the problem in more detail and with some
> observations.  I will be very grateful if someone can come up with
> ideas of how to fix this or give me some ideas that can lead to a
> solution.  Not only Xen has this problem, but so has FreeBSD and
> NetBSD, so a solution will be beneficial to these projects as well.
> 
> What happens is the following: The first core sends two IPI
> messages(INIT and STARTUP) to start the second core.  When the second
> core is started, it notifies the first core of this so it can continue
> with the boot process.  However, the second core is not started by
> these messages, the loop that waits for the second core times out,
> continues and Xen crashes.
> 
> One strange thing is that Xen initializes the second core properly
> when you press a key on the keyboard after the IPIs are sent.  I am
> expecting this interrupt somehow wakes up the second core so it can
> accept and process the IPIs.  Because it is a laptop the second core
> is put in deep sleep mode to save power in case an OS does not use
> this core at all.  But as I understand it, it should wake up when an
> INIT IPI arrives.
> 
> The problems I am having with Xen can be reproduced with linux when
> booting with "acpi=ht", which means the ACPI interpreter is not
> started.
> 
> Hopefully someone has some ideas how to deal with this issue and how
> to properly fix this.  If you want more information or want me to test
> things, feel free to ask.
> 
> Thanks,
> Marco
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
> 


[-- Attachment #2: intelmac_grub.diff --]
[-- Type: text/x-patch, Size: 1246 bytes --]

--- grub-0.97.orig/stage2/asm.S	2004-06-19 18:55:22.000000000 +0200
+++ grub-0.97/stage2/asm.S	2006-04-21 11:10:52.000000000 +0200
@@ -1651,7 +1651,29 @@
 	jnz	3f
 	ret
 
-3:	/* use keyboard controller */
+3:	/*
+	 * try to switch gateA20 using PORT92, the "Fast A20 and Init"
+	 * register
+	*/
+	mov $0x92, %dx
+	inb %dx, %al
+	/* skip the port92 code if it's unimplemented (read returns 0xff) */
+	cmpb $0xff, %al
+	jz 6f
+	
+	/* set or clear bit1, the ALT_A20_GATE bit */
+	movb 4(%esp), %ah
+	testb %ah, %ah
+	jz 4f
+	orb $2, %al
+	jmp 5f
+4:	and $0xfd, %al
+	
+	/* clear the INIT_NOW bit don't accidently reset the machine */
+5:	and $0xfe, %al
+	outb %al, %dx
+	
+6:	/* use keyboard controller */
 	pushl	%eax
 
 	call    gloop1
@@ -1661,9 +1683,12 @@
 
 gloopint1:
 	inb	$K_STATUS
+	cmpb	$0xff, %al
+	jz	gloopint1_done
 	andb	$K_IBUF_FUL, %al
 	jnz	gloopint1
 
+gloopint1_done:	
 	movb	$KB_OUTPUT_MASK, %al
 	cmpb	$0, 0x8(%esp)
 	jz	gdoit
@@ -1684,6 +1709,8 @@
 
 gloop1:
 	inb	$K_STATUS
+	cmpb	$0xff, %al
+	jz	gloop2ret
 	andb	$K_IBUF_FUL, %al
 	jnz	gloop1
 
@@ -1991,6 +2018,11 @@
 ENTRY(console_getkey)
 	push	%ebp
 
+wait_for_key:
+	call	EXT_C(console_checkkey)
+	incl	%eax
+	jz	wait_for_key
+	
 	call	EXT_C(prot_to_real)
 	.code16
 

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