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Date: Mon, 13 Mar 2006 10:04:23 -0800
Message-Id: <200603131804.k2DI4N6s005678@zach-dev.vmware.com>
Subject: [RFC, PATCH 7/24] i386 Vmi memory hole
From: Zachary Amsden <zach@vmware.com>
To: Linus Torvalds <torvalds@osdl.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Virtualization Mailing List <virtualization@lists.osdl.org>,
       Xen-devel <xen-devel@lists.xensource.com>,
       Andrew Morton <akpm@osdl.org>, Zachary Amsden <zach@vmware.com>,
       Dan Hecht <dhecht@vmware.com>, Dan Arai <arai@vmware.com>,
       Anne Holler <anne@vmware.com>, Pratap Subrahmanyam <pratap@vmware.com>,
       Christopher Li <chrisl@vmware.com>, Joshua LeVasseur <jtl@ira.uka.de>,
       Chris Wright <chrisw@osdl.org>, Rik Van Riel <riel@redhat.com>,
       Jyothy Reddy <jreddy@vmware.com>, Jack Lo <jlo@vmware.com>,
       Kip Macy <kmacy@fsmware.com>, Jan Beulich <jbeulich@novell.com>,
       Ky Srinivasan <ksrinivasan@novell.com>,
       Wim Coekaerts <wim.coekaerts@oracle.com>,
       Leendert van Doorn <leendert@watson.ibm.com>,
       Zachary Amsden <zach@vmware.com>
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Create a configurable hole in the linear address space at the top
of memory.  A more advanced interface is needed to negotiate how
much space the hypervisor is allowed to steal, but in the end, it
seems most likely that a fixed constant size will be chosen for
the compiled kernel, potentially propagated to an information
page used by paravirtual initialization to determine interface
compatibility.

Signed-off-by: Zachary Amsden <zach@vmware.com>

Index: linux-2.6.16-rc3/arch/i386/Kconfig
===================================================================
--- linux-2.6.16-rc3.orig/arch/i386/Kconfig	2006-02-22 16:09:04.000000000 -0800
+++ linux-2.6.16-rc3/arch/i386/Kconfig	2006-02-22 16:33:27.000000000 -0800
@@ -201,6 +201,15 @@ config VMI_DEBUG
 
 endmenu
 
+config MEMORY_HOLE
+	int "Create hole at top of memory (0-256 MB)"
+	range 0 256
+	default "64" if X86_VMI
+	default "0" if !X86_VMI
+	help
+	   Useful for creating a hole in the top of memory when running
+	   inside of a virtual machine monitor.
+
 config ACPI_SRAT
 	bool
 	default y
Index: linux-2.6.16-rc3/include/asm-i386/fixmap.h
===================================================================
--- linux-2.6.16-rc3.orig/include/asm-i386/fixmap.h	2006-02-22 15:48:23.000000000 -0800
+++ linux-2.6.16-rc3/include/asm-i386/fixmap.h	2006-02-22 16:33:27.000000000 -0800
@@ -20,7 +20,7 @@
  * Leave one empty page between vmalloc'ed areas and
  * the start of the fixmap.
  */
-#define __FIXADDR_TOP	0xfffff000
+#define __FIXADDR_TOP	0xfffff000-(CONFIG_MEMORY_HOLE << 20)
 
 #ifndef __ASSEMBLY__
 #include <linux/kernel.h>
-
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