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Message-ID: <20060802070147.GM2654@sequoia.sous-sol.org>
Date: Wed, 2 Aug 2006 00:01:47 -0700
From: Chris Wright <chrisw@...s-sol.org>
To: Rusty Russell <rusty@...tcorp.com.au>
Cc: Chris Wright <chrisw@...s-sol.org>, Andrew Morton <akpm@...l.org>,
jeremy@...source.com, linux-kernel@...r.kernel.org,
Christian.Limpach@...cam.ac.uk, clameter@....com,
ebiederm@...ssion.com, kraxel@...e.de, hollisb@...ibm.com,
ian.pratt@...source.com, zach@...are.com
Subject: Re: [PATCH 7 of 13] Make __FIXADDR_TOP variable to allow it to make space for a hypervisor
* Rusty Russell (rusty@...tcorp.com.au) wrote:
> On Tue, 2006-08-01 at 14:37 -0700, Chris Wright wrote:
> > * Andrew Morton (akpm@...l.org) wrote:
> > > On Tue, 1 Aug 2006 02:03:30 -0700
> > > Chris Wright <chrisw@...s-sol.org> wrote:
> > >
> > > > * Jeremy Fitzhardinge (jeremy@...source.com) wrote:
> > > > > -#define MAXMEM (-__PAGE_OFFSET-__VMALLOC_RESERVE)
> > > > > +#define MAXMEM (__FIXADDR_TOP-__PAGE_OFFSET-__VMALLOC_RESERVE)
> > > >
> > > > In the native case we lose one page of lowmem now.
> > >
> > > erm, isn't this the hunk which gave one of my machines a 4kb highmem zone?
> > > I have memories of reverting it.
> >
> > Yes, that does sound quite familiar. I couldn't find the thread, do you
> > recall any of the details? I expect it's the same issue as the off by one
> > page I mentioned above.
>
> Good catch Andrew. I did say we'd fix this. Will frob this patch
> further...
Here's an updated patch. Rather than use __FIXADDR_TOP to adjust for
MAXMEM, directly update __VMALLOC_RESERVE which is used to reserve the
space for vmalloc, iomap, and fixmap (as comments aptly point out). I
tested this with a bunch of configurations, and booted a XenoLinux
kernel with this patch as well.
thanks,
-chris
--
Make __FIXADDR_TOP variable to allow it to make space for a hypervisor.
Make __FIXADDR_TOP a variable, so that it can be set to not get in the
way of address space a hypervisor may want to reserve.
Original patch by Gerd Hoffmann <kraxel@...e.de>
Signed-off-by: Jeremy Fitzhardinge <jeremy@...source.com>
Signed-off-by: Chris Wright <chrisw@...s-sol.org>
Cc: Gerd Hoffmann <kraxel@...e.de>
---
arch/i386/Kconfig | 1 +
arch/i386/mm/init.c | 42 ++++++++++++++++++++++++++++++++++++++++++
arch/i386/mm/pgtable.c | 19 +++++++++++++++++++
include/asm-i386/fixmap.h | 7 ++++++-
4 files changed, 68 insertions(+), 1 deletion(-)
diff -r 5183f1f33cf4 arch/i386/Kconfig
--- a/arch/i386/Kconfig Tue Aug 01 01:06:48 2006 -0400
+++ b/arch/i386/Kconfig Wed Aug 02 02:34:44 2006 -0400
@@ -792,6 +792,7 @@ config COMPAT_VDSO
config COMPAT_VDSO
bool "Compat VDSO support"
default y
+ depends on !PARAVIRT
help
Map the VDSO to the predictable old-style address too.
---help---
diff -r 5183f1f33cf4 arch/i386/mm/init.c
--- a/arch/i386/mm/init.c Tue Aug 01 01:06:48 2006 -0400
+++ b/arch/i386/mm/init.c Wed Aug 02 02:34:44 2006 -0400
@@ -629,6 +629,48 @@ void __init mem_init(void)
(unsigned long) (totalhigh_pages << (PAGE_SHIFT-10))
);
+#if 1 /* double-sanity-check paranoia */
+ printk("virtual kernel memory layout:\n"
+ " fixmap : 0x%08lx - 0x%08lx (%4ld kB)\n"
+#ifdef CONFIG_HIGHMEM
+ " pkmap : 0x%08lx - 0x%08lx (%4ld kB)\n"
+#endif
+ " vmalloc : 0x%08lx - 0x%08lx (%4ld MB)\n"
+ " lowmem : 0x%08lx - 0x%08lx (%4ld MB)\n"
+ " .init : 0x%08lx - 0x%08lx (%4ld kB)\n"
+ " .data : 0x%08lx - 0x%08lx (%4ld kB)\n"
+ " .text : 0x%08lx - 0x%08lx (%4ld kB)\n",
+ FIXADDR_START, FIXADDR_TOP,
+ (FIXADDR_TOP - FIXADDR_START) >> 10,
+
+#ifdef CONFIG_HIGHMEM
+ PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE,
+ (LAST_PKMAP*PAGE_SIZE) >> 10,
+#endif
+
+ VMALLOC_START, VMALLOC_END,
+ (VMALLOC_END - VMALLOC_START) >> 20,
+
+ (unsigned long)__va(0), (unsigned long)high_memory,
+ ((unsigned long)high_memory - (unsigned long)__va(0)) >> 20,
+
+ (unsigned long)&__init_begin, (unsigned long)&__init_end,
+ ((unsigned long)&__init_end - (unsigned long)&__init_begin) >> 10,
+
+ (unsigned long)&_etext, (unsigned long)&_edata,
+ ((unsigned long)&_edata - (unsigned long)&_etext) >> 10,
+
+ (unsigned long)&_text, (unsigned long)&_etext,
+ ((unsigned long)&_etext - (unsigned long)&_text) >> 10);
+
+#ifdef CONFIG_HIGHMEM
+ BUG_ON(PKMAP_BASE+LAST_PKMAP*PAGE_SIZE > FIXADDR_START);
+ BUG_ON(VMALLOC_END > PKMAP_BASE);
+#endif
+ BUG_ON(VMALLOC_START > VMALLOC_END);
+ BUG_ON((unsigned long)high_memory > VMALLOC_START);
+#endif /* double-sanity-check paranoia */
+
#ifdef CONFIG_X86_PAE
if (!cpu_has_pae)
panic("cannot execute a PAE-enabled kernel on a PAE-less CPU!");
diff -r 5183f1f33cf4 arch/i386/mm/pgtable.c
--- a/arch/i386/mm/pgtable.c Tue Aug 01 01:06:48 2006 -0400
+++ b/arch/i386/mm/pgtable.c Wed Aug 02 02:34:44 2006 -0400
@@ -12,6 +12,7 @@
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/spinlock.h>
+#include <linux/module.h>
#include <asm/system.h>
#include <asm/pgtable.h>
@@ -137,6 +138,12 @@ void set_pmd_pfn(unsigned long vaddr, un
__flush_tlb_one(vaddr);
}
+static int fixmaps;
+#ifndef CONFIG_COMPAT_VDSO
+unsigned long __FIXADDR_TOP = 0xfffff000;
+EXPORT_SYMBOL(__FIXADDR_TOP);
+#endif
+
void __set_fixmap (enum fixed_addresses idx, unsigned long phys, pgprot_t flags)
{
unsigned long address = __fix_to_virt(idx);
@@ -146,6 +153,18 @@ void __set_fixmap (enum fixed_addresses
return;
}
set_pte_pfn(address, phys >> PAGE_SHIFT, flags);
+ fixmaps++;
+}
+
+void set_fixaddr_top(unsigned long top)
+{
+ BUG_ON(fixmaps > 0);
+#ifdef CONFIG_COMPAT_VDSO
+ BUG_ON(top - PAGE_SIZE != __FIXADDR_TOP);
+#else
+ __FIXADDR_TOP = top - PAGE_SIZE;
+ __VMALLOC_RESERVE -= top;
+#endif
}
pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
diff -r 5183f1f33cf4 include/asm-i386/fixmap.h
--- a/include/asm-i386/fixmap.h Tue Aug 01 01:06:48 2006 -0400
+++ b/include/asm-i386/fixmap.h Wed Aug 02 02:34:44 2006 -0400
@@ -19,7 +19,11 @@
* Leave one empty page between vmalloc'ed areas and
* the start of the fixmap.
*/
-#define __FIXADDR_TOP 0xfffff000
+#ifndef CONFIG_COMPAT_VDSO
+extern unsigned long __FIXADDR_TOP;
+#else
+#define __FIXADDR_TOP 0xfffff000
+#endif
#ifndef __ASSEMBLY__
#include <linux/kernel.h>
@@ -93,6 +97,7 @@ enum fixed_addresses {
extern void __set_fixmap (enum fixed_addresses idx,
unsigned long phys, pgprot_t flags);
+extern void set_fixaddr_top(unsigned long top);
#define set_fixmap(idx, phys) \
__set_fixmap(idx, phys, PAGE_KERNEL)
-
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