2.6.23: does it supposed to work on an i486?

2.6.23: does it supposed to work on an i486?

[Michael Tokarev]

I tried to upgrade one of our ooooold machines
(used as print servers and similar tasks) today
from 2.6.22 to 2.6.23[.9].  The same config (with
minor tweaks for new options), i486 base arch,
X86_GENERIC=y.

The result is immediately machine reboot right
after bootloader (etherboot) passes control to
the kernel -- BEFORE "Uncompressing linux"
message.

2.6.22 worked just fine.

So I wonder if it's supposed to work in the first
place.  The thing is that this machine(s) are very
slow to boot, so trying to figure out which change
is at question will require quite some time...

Thanks.

/mjt

Re: 2.6.23: does it supposed to work on an i486?

[H. Peter Anvin]

[-- Attachment #1: Type: text/plain, Size: 802 bytes --]

Michael Tokarev wrote:
> I tried to upgrade one of our ooooold machines
> (used as print servers and similar tasks) today
> from 2.6.22 to 2.6.23[.9].  The same config (with
> minor tweaks for new options), i486 base arch,
> X86_GENERIC=y.
> 
> The result is immediately machine reboot right
> after bootloader (etherboot) passes control to
> the kernel -- BEFORE "Uncompressing linux"
> message.
> 
> 2.6.22 worked just fine.
> 
> So I wonder if it's supposed to work in the first
> place.  The thing is that this machine(s) are very
> slow to boot, so trying to figure out which change
> is at question will require quite some time...

It looks like 2.6.23.9 is missing checkin 
7ed192906a2144ebc8ca2925a85d27b9c5355668 from Linus' tree (attached), 
which is necessary to work on 386 and 486.

	-hpa

[-- Attachment #2: 0001-x86-setup-add-a-near-jump-to-serialize-cr0-on-386.patch --]
[-- Type: text/x-patch, Size: 1046 bytes --]

>From 7ed192906a2144ebc8ca2925a85d27b9c5355668 Mon Sep 17 00:00:00 2001
From: H. Peter Anvin <hpa@zytor.com>
Date: Sun, 4 Nov 2007 17:50:12 -0800
Subject: [PATCH] x86 setup: add a near jump to serialize %cr0 on 386/486

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>
---
 arch/x86/boot/pmjump.S |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/pmjump.S b/arch/x86/boot/pmjump.S
index 2e55923..26baeab 100644
--- a/arch/x86/boot/pmjump.S
+++ b/arch/x86/boot/pmjump.S
@@ -31,14 +31,14 @@ protected_mode_jump:
 	xorl	%ebx, %ebx		# Flag to indicate this is a boot
 	movl	%edx, %esi		# Pointer to boot_params table
 	movl	%eax, 2f		# Patch ljmpl instruction
-	jmp	1f			# Short jump to flush instruction q.
 
-1:
 	movw	$__BOOT_DS, %cx
 
 	movl	%cr0, %edx
 	orb	$1, %dl			# Protected mode (PE) bit
 	movl	%edx, %cr0
+	jmp	1f			# Short jump to serialize on 386/486
+1:
 
 	movw	%cx, %ds
 	movw	%cx, %es
-- 
1.5.3.4

Re: 2.6.23: does it supposed to work on an i486?

[Michael Tokarev]

H. Peter Anvin wrote:
> Michael Tokarev wrote:
[2.6.23 on an i486 machine]
>> The result is immediately machine reboot right
>> after bootloader (etherboot) passes control to
>> the kernel -- BEFORE "Uncompressing linux"
>> message.
>>
>> 2.6.22 worked just fine.
[]
> It looks like 2.6.23.9 is missing checkin
> 7ed192906a2144ebc8ca2925a85d27b9c5355668 from Linus' tree (attached),
> which is necessary to work on 386 and 486.

Well, I applied the patch (in 2.6.23 it's
 arch/i386/boot/pmjump.S,
not
 arch/x86/boot/pmjump.S,
but that's minor) - still the same behavior, it still reboots
instantly right when bootloader gave control to the kernel.
So it must be something else.. ;)

I'll try other kernels tomorrow, given some time (I already
spent almost the whole day today with this "machine").  This
whole story prompted me to just throw those machines away and
replace them with tiny devices (a small print server in this
case).  There are still several 486-class machines out there...

By the way, this very machine I'm experimenting with is a
strange beast by itself.  For example, etherboot does not
work on it properly, anything since version 5.1.0 just
freezes right after displaying the "greeting" message.
5.0.11 works.  However till now, linux worked on it just
fine, -- unlike etherboot.

Thanks!

/mjt

Re: 2.6.23: does it supposed to work on an i486?

[H. Peter Anvin]

Michael Tokarev wrote:
>> It looks like 2.6.23.9 is missing checkin
>> 7ed192906a2144ebc8ca2925a85d27b9c5355668 from Linus' tree (attached),
>> which is necessary to work on 386 and 486.
> 
> Well, I applied the patch (in 2.6.23 it's
>  arch/i386/boot/pmjump.S,
> not
>  arch/x86/boot/pmjump.S,
> but that's minor) - still the same behavior, it still reboots
> instantly right when bootloader gave control to the kernel.
> So it must be something else.. ;)

Well, it's a good bet it's croaking somewhere in the setup code 
(arch/{i386,x86}/boot).  Putting debugging statements there might help.

	-hpa

Re: 2.6.23: does it supposed to work on an i486?

[Gerb Stralko]

> Well, I applied the patch (in 2.6.23 it's
>  arch/i386/boot/pmjump.S,
> not
>  arch/x86/boot/pmjump.S,
> but that's minor) - still the same behavior, it still reboots
> instantly right when bootloader gave control to the kernel.
> So it must be something else.. ;)

It should be x86, they merged the i386 and x86_64 code into one arch
called x86.   Try it again and see if it works

Thanks,

- Jerry