Message-ID: <20080613023348.GA6071@localdomain>
Date:	Thu, 12 Jun 2008 19:33:48 -0700
From:	Ravikiran G Thirumalai <kiran@...lex86.org>
To:	stable@...nel.org
Cc:	linux-kernel@...r.kernel.org, zippel@...ux-m68k.org,
	sam@...nborg.org, shai@...lex86.org
Subject: [2.6.25 - stable] Fix Kconfig dependencies to prevent
	CONFIG_X86_VSMP from vanishing

There was a Kconfig bug found sometime back which made CONFIG_X86_VSMP
disappear from the .config.  The bug description is as follows:

On a linux-2.6.25.6 source tree, x86_64 arch,

1. Use make menuconfig to select "Processor type and features" menu
2. Change  Subarchitecture type  from "PC-Compatible" to
   "Support for ScaleMP vSMP"
3. Exit and save configuration.  Make sure CONFIG_X86_VSMP is selected in
   .config
4. Build the kernel and recheck the .config for CONFIG_X86_VSMP --
   CONFIG_X86_VSMP disappeared!  However, vsmp bits get built and linked
   in.  On booting up the resulting  kernel on a ScaleMP vSMPowered machine,
   dmesg shows   printks that ought to happen if CONFIG_X86_VSMP is set, however,
   /proc/config.gz says CONFIG_X86_VSMP is unset!  The inter-node cacheline
   setting (CONFIG_X86_INTERNODE_CACHE_BYTE) which is dependent on
   CONFIG_X86_VSMP is not set correctly in /proc/config.gz either.  Hence,
   we can't be sure if INTERNODE_CACHE_BYTE is set correctly
5. Running 'make oldconfig' or 'make menuconfig' again after 3. causes
   CONFIG_X86_VSMP to vanish.

This bug was reported sometime back and fixed in x86 tree and eventually in
2.6.26-rc.
The original bug report can be found at:
	http://lkml.org/lkml/2008/2/26/318

The fixes were posted by Roman in the same thread:
	http://lkml.org/lkml/2008/2/28/575

The fixes consisted of 3 patches, but the first one is sufficient to fix the
problem in 2.6.25

The commits in mainline for the fix are:
	823c248e7cc75b4f22da914b01f8e5433cff197e
	48981178869bf7d9770f11fc361996ad11217a75
	5a1aa8a1aff6191ecc55f21d8b5f0e47108ed91b

Please consider a trimmed down version of the first patch --
823c248e7cc75b4f22da914b01f8e5433cff197e, which is sufficient to fix
the CONFIG_X86_VSMP disappearance for stable release.  CONFIG_X86_VSMP
has been well supported and working well since 2.6.16.  Not able to choose
CONFIG_X86_VSMP reliably is a major regression.  Users compiling
kernel.org 2.6.25 kernel for vSMP have been reporting problems which are
mainly due to CONFIG_X86_VSMP disappearing.  In addition /proc/config.gz
mismatch due to the bug is a major PITA.

I am including a trimmed down patch of
823c248e7cc75b4f22da914b01f8e5433cff197e to fix CONFIG_VSMP as per
stable policy.  This was tested and found to fix the problem mentioned
above.  Please apply.

Thanks,
Kiran

---

x86: fix recursive dependencies with CONFIG_VSMP

Trimmed down version of the commit
823c248e7cc75b4f22da914b01f8e5433cff197e

Originally-by: Roman Zippel <zippel@...ux-m68k.org>

Signed-off-by: Ravikiran Thirumalai <kiran@...lex86.org>

Index: linux-2.6.25.6/arch/x86/Kconfig
===================================================================
--- linux-2.6.25.6.orig/arch/x86/Kconfig	2008-06-12 18:09:37.000000000 -0700
+++ linux-2.6.25.6/arch/x86/Kconfig	2008-06-12 18:25:04.000000000 -0700
@@ -339,7 +339,7 @@ config X86_RDC321X
 
 config X86_VSMP
 	bool "Support for ScaleMP vSMP"
-	depends on X86_64 && PCI
+	depends on X86_64
 	 help
 	  Support for ScaleMP vSMP systems.  Say 'Y' here if this kernel is
 	  supposed to run on these EM64T-based machines.  Only choose this option
@@ -1391,7 +1391,7 @@ endmenu
 menu "Bus options (PCI etc.)"
 
 config PCI
-	bool "PCI support" if !X86_VISWS
+	bool "PCI support" if !X86_VISWS && !X86_VSMP
 	depends on !X86_VOYAGER
 	default y
 	select ARCH_SUPPORTS_MSI if (X86_LOCAL_APIC && X86_IO_APIC)
--
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