could save some bit shifting operations.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-38-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

to replace own inline version for shifting.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-37-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

to replace own inline version for those roundup and rounddown.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-36-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Put it in mm/init.c, and call it from probe_page_mask().
init_mem_mapping is calling probe_page_mask at first.
So calling sequence is not changed.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-32-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Also change them to static.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-31-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

On 32bit, before patcheset that only set page table for ram, we only
call that one time.

Now, we are calling that during every init_memory_mapping if we have holes
under max_low_pfn.

We should only call it one time after all ranges under max_low_page get
mapped just like we did before.

Also that could avoid the risk to run out of pgt_buf in BRK.

Need to update page_table_range_init() to count the pages for kmap page table
at first, and use new added alloc_low_pages() to get pages in sequence.
That will conform to the requirement that pages need to be in low to high order.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-30-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Add link for more information
	279b706b x86,xen: introduce x86_init.mapping.pagetable_reserve

-v2: updated to commets from hpa to include commit name.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-29-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

32bit kmap mapping needs pages to be used for low to high.
At this point those pages are still from pgt_buf_* from BRK, so it is
ok now.
But we want to move early_ioremap_page_table_range_init() out of
init_memory_mapping() and only call it one time later, that will
make page_table_range_init/page_table_kmap_check/alloc_low_page to
use memblock to get page.

memblock allocation for pages are from high to low.
So will get panic from page_table_kmap_check() that has BUG_ON to do
ordering checking.

This patch add alloc_low_pages to make it possible to allocate serveral
pages at first, and hand out pages one by one from low to high.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-28-git-send-email-yinghai@kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Page table area are pre-mapped now after
	x86, mm: setup page table in top-down
	x86, mm: Remove early_memremap workaround for page table accessing on 64bit

mapping_pagetable_reserve is not used anymore, so remove it.

Also remove operation in mask_rw_pte(), as modified allow_low_page
always return pages that are already mapped, moreover
xen_alloc_pte_init, xen_alloc_pmd_init, etc, will mark the page RO
before hooking it into the pagetable automatically.

-v2: add changelog about mask_rw_pte() from Stefano.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-27-git-send-email-yinghai@kernel.org
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Also change it to static.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-26-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

They are almost same except 64 bit need to handle after_bootmem case.

Add mm_internal.h to make that alloc_low_page() only to be accessible
from arch/x86/mm/init*.c
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-25-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Get pgt_buf early from BRK, and use it to map PMD_SIZE from top at first.
Then use mapped pages to map more ranges below, and keep looping until
all pages get mapped.

alloc_low_page will use page from BRK at first, after that buffer is used
up, will use memblock to find and reserve pages for page table usage.

Introduce min_pfn_mapped to make sure find new pages from mapped ranges,
that will be updated when lower pages get mapped.

Also add step_size to make sure that don't try to map too big range with
limited mapped pages initially, and increase the step_size when we have
more mapped pages on hand.

We don't need to call pagetable_reserve anymore, reserve work is done
in alloc_low_page() directly.

At last we can get rid of calculation and find early pgt related code.

-v2: update to after fix_xen change,
     also use MACRO for initial pgt_buf size and add comments with it.
-v3: skip big reserved range in memblock.reserved near end.
-v4: don't need fix_xen change now.
-v5: add changelog about moving about reserving pagetable to alloc_low_page.
Suggested-by: N"H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-22-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Will replace that with top-down page table initialization.
New API need to take range: init_range_memory_mapping()
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-21-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

We could map small range in the middle of big range at first, so should use
big page size at first to avoid using small page size to break down page table.

Only can set big page bit when that range has ram area around it.

-v2: fix 32bit boundary checking. We can not count ram above max_low_pfn
	for 32 bit.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-19-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Currently direct mappings are created for [ 0 to max_low_pfn<<PAGE_SHIFT )
and [ 4GB to max_pfn<<PAGE_SHIFT ), which may include regions that are not
backed by actual DRAM. This is fine for holes under 4GB which are covered
by fixed and variable range MTRRs to be UC. However, we run into trouble
on higher memory addresses which cannot be covered by MTRRs.

Our system with 1TB of RAM has an e820 that looks like this:

 BIOS-e820: [mem 0x0000000000000000-0x00000000000983ff] usable
 BIOS-e820: [mem 0x0000000000098400-0x000000000009ffff] reserved
 BIOS-e820: [mem 0x00000000000d0000-0x00000000000fffff] reserved
 BIOS-e820: [mem 0x0000000000100000-0x00000000c7ebffff] usable
 BIOS-e820: [mem 0x00000000c7ec0000-0x00000000c7ed7fff] ACPI data
 BIOS-e820: [mem 0x00000000c7ed8000-0x00000000c7ed9fff] ACPI NVS
 BIOS-e820: [mem 0x00000000c7eda000-0x00000000c7ffffff] reserved
 BIOS-e820: [mem 0x00000000fec00000-0x00000000fec0ffff] reserved
 BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved
 BIOS-e820: [mem 0x00000000fff00000-0x00000000ffffffff] reserved
 BIOS-e820: [mem 0x0000000100000000-0x000000e037ffffff] usable
 BIOS-e820: [mem 0x000000e038000000-0x000000fcffffffff] reserved
 BIOS-e820: [mem 0x0000010000000000-0x0000011ffeffffff] usable

and so direct mappings are created for huge memory hole between
0x000000e038000000 to 0x0000010000000000. Even though the kernel never
generates memory accesses in that region, since the page tables mark
them incorrectly as being WB, our (AMD) processor ends up causing a MCE
while doing some memory bookkeeping/optimizations around that area.

This patch iterates through e820 and only direct maps ranges that are
marked as E820_RAM, and keeps track of those pfn ranges. Depending on
the alignment of E820 ranges, this may possibly result in using smaller
size (i.e. 4K instead of 2M or 1G) page tables.

-v2: move changes from setup.c to mm/init.c, also use for_each_mem_pfn_range
	instead.  - Yinghai Lu
-v3: add calculate_all_table_space_size() to get correct needed page table
	size. - Yinghai Lu
-v4: fix add_pfn_range_mapped() to get correct max_low_pfn_mapped when
     mem map does have hole under 4g that is found by Konard on xen
     domU with 8g ram. - Yinghai
Signed-off-by: NJacob Shin <jacob.shin@amd.com>
Link: http://lkml.kernel.org/r/1353123563-3103-16-git-send-email-yinghai@kernel.orgSigned-off-by: NYinghai Lu <yinghai@kernel.org>
Reviewed-by: NPekka Enberg <penberg@kernel.org>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

It should take physical address range that will need to be mapped.
find_early_table_space should take range that pgt buff should be in.

Separating page table size calculating and finding early page table to
reduce confusing.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-9-git-send-email-yinghai@kernel.orgReviewed-by: NPekka Enberg <penberg@kernel.org>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

We should not do that in every calling of init_memory_mapping.

At the same time need to move down early_memtest, and could remove after_bootmem
checking.

-v2: fix one early_memtest with 32bit by passing max_pfn_mapped instead.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-8-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

call split_mem_range inside the function.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-7-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

After

| commit 8548c84d
| Author: Takashi Iwai <tiwai@suse.de>
| Date:   Sun Oct 23 23:19:12 2011 +0200
|
|    x86: Fix S4 regression
|
|    Commit 4b239f45 ("x86-64, mm: Put early page table high") causes a S4
|    regression since 2.6.39, namely the machine reboots occasionally at S4
|    resume.  It doesn't happen always, overall rate is about 1/20.  But,
|    like other bugs, once when this happens, it continues to happen.
|
|    This patch fixes the problem by essentially reverting the memory
|    assignment in the older way.

Have some page table around 512M again, that will prevent kdump to find 512M
under 768M.

We need revert that reverting, so we could put page table high again for 64bit.

Takashi agreed that S4 regression could be something else.

	https://lkml.org/lkml/2012/6/15/182Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-6-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Now init_memory_mapping is called two times, later will be called for every
ram ranges.

Could put all related init_mem calling together and out of setup.c.

Actually, it reverts commit 1bbbbe77
    x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping.
will address that later with complete solution include handling hole under 4g.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-5-git-send-email-yinghai@kernel.orgReviewed-by: NPekka Enberg <penberg@kernel.org>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

It will need to call split_mem_range().
Move it down after that to avoid extra declaration.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-4-git-send-email-yinghai@kernel.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

So make init_memory_mapping smaller and readable.

-v2: use 0 instead of nr_range as input parameter found by Yasuaki Ishimatsu.
Suggested-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-3-git-send-email-yinghai@kernel.orgReviewed-by: NPekka Enberg <penberg@kernel.org>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Now we pass around use_gbpages and use_pse for calculating page table size,
Later we will need to call init_memory_mapping for every ram range one by one,
that mean those calculation will be done several times.

Those information are the same for all ram range and could be stored in
page_size_mask and could be probed it one time only.

Move that probing code out of init_memory_mapping into separated function
probe_page_size_mask(), and call it before all init_memory_mapping.
Suggested-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1353123563-3103-2-git-send-email-yinghai@kernel.orgReviewed-by: NPekka Enberg <penberg@kernel.org>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Commit

    844ab6f9 x86, mm: Find_early_table_space based on ranges that are actually being mapped

added back some lines back wrongly that has been removed in commit

    7b16bbf9 Revert "x86/mm: Fix the size calculation of mapping tables"

remove them again.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/CAE9FiQW_vuaYQbmagVnxT2DGsYc=9tNeAbdBq53sYkitPOwxSQ@mail.gmail.comAcked-by: NJacob Shin <jacob.shin@amd.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Current logic finds enough space for direct mapping page tables from 0
to end. Instead, we only need to find enough space to cover mr[0].start
to mr[nr_range].end -- the range that is actually being mapped by
init_memory_mapping()

This is needed after 1bbbbe77, to address
the panic reported here:

  https://lkml.org/lkml/2012/10/20/160
  https://lkml.org/lkml/2012/10/21/157Signed-off-by: NJacob Shin <jacob.shin@amd.com>
Link: http://lkml.kernel.org/r/20121024195311.GB11779@jshin-ToonieTested-by: NTom Rini <trini@ti.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Commit:

   722bc6b1 x86/mm: Fix the size calculation of mapping tables

Tried to address the issue that the first 2/4M should use 4k pages
if PSE enabled, but extra counts should only be valid for x86_32.

This commit caused a kdump regression: the kdump kernel hangs.

Work is in progress to fundamentally fix the various page table
initialization issues that we have, via the design suggested
by H. Peter Anvin, but it's not ready yet to be merged.

So, to get a working kdump revert to the last known working version,
which is the revert of this commit and of a followup fix (which was
incomplete):

   bd2753b2 x86/mm: Only add extra pages count for the first memory range during pre-allocation

Tested kdump on physical and virtual machines.
Signed-off-by: NDave Young <dyoung@redhat.com>
Acked-by: NYinghai Lu <yinghai@kernel.org>
Acked-by: NCong Wang <xiyou.wangcong@gmail.com>
Acked-by: NFlavio Leitner <fbl@redhat.com>
Tested-by: NFlavio Leitner <fbl@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Flavio Leitner <fbl@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: ianfang.cn@gmail.com
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@kernel.org>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Fixing an off-by-one error in devmem_is_allowed(), which allows
accesses to physical addresses 0x100000-0x100fff, an extra page
past 1MB.
Signed-off-by: NT Makphaibulchoke <tmac@hp.com>
Acked-by: NH. Peter Anvin <hpa@zytor.com>
Cc: yinghai@kernel.org
Cc: tiwai@suse.de
Cc: dhowells@redhat.com
Link: http://lkml.kernel.org/r/1346210503-14276-1-git-send-email-tmac@hp.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

... matching various other architectures.
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/4FDF1F5C020000780008A661@nat28.tlf.novell.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

x86/mm: Only add extra pages count for the first memory range during pre-allocation early page table space

Robin found this regression:

| I just tried to boot an 8TB system.  It fails very early in boot with:
| Kernel panic - not syncing: Cannot find space for the kernel page tables

git bisect commit 722bc6b1.

A git revert of that commit does boot past that point on the 8TB
configuration.

That commit will add up extra pages for all memory range even
above 4g.

Try to limit that extra page count adding to first entry only.
Bisected-by: NRobin Holt <holt@sgi.com>
Tested-by: NRobin Holt <holt@sgi.com>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/CAE9FiQUj3wyzQxtq9yzBNc9u220p8JZ1FYHG7t%3DMOzJ%3D9BZMYA@mail.gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Print physical address info in a style consistent with the %pR style used
elsewhere in the kernel.  For example:

    -found SMP MP-table at [ffff8800000fce90] fce90
    +found SMP MP-table at [mem 0x000fce90-0x000fce9f] mapped at [ffff8800000fce90]
    -initial memory mapped : 0 - 20000000
    +initial memory mapped: [mem 0x00000000-0x1fffffff]
    -Base memory trampoline at [ffff88000009c000] 9c000 size 8192
    +Base memory trampoline [mem 0x0009c000-0x0009dfff] mapped at [ffff88000009c000]
    -SRAT: Node 0 PXM 0 0-80000000
    +SRAT: Node 0 PXM 0 [mem 0x00000000-0x7fffffff]
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Disintegrate asm/system.h for X86.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NH. Peter Anvin <hpa@zytor.com>
cc: x86@kernel.org

For machines that enable PSE, the first 2/4M memory region still uses
4K pages, so needs more PTEs in this case, but
find_early_table_space() doesn't count this.

This patch fixes it.

The bug was found via code review, no misbehavior of the kernel
was observed.
Signed-off-by: NWANG Cong <xiyou.wangcong@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: <ianfang.cn@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-kq6a00qe33h7c7ais2xsywnh@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>

Now that zone_sizes_init() is identical on 32-bit and 64-bit,
move the code to arch/x86/mm/init.c and use it for both
architectures.
Acked-by: NTejun Heo <tj@kernel.org>
Acked-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NPekka Enberg <penberg@kernel.org>
Link: http://lkml.kernel.org/r/1320155902-10424-7-git-send-email-penberg@kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>

Commit 4b239f45 ("x86-64, mm: Put early page table high") causes a S4
regression since 2.6.39, namely the machine reboots occasionally at S4
resume.  It doesn't happen always, overall rate is about 1/20.  But,
like other bugs, once when this happens, it continues to happen.

This patch fixes the problem by essentially reverting the memory
assignment in the older way.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Cc: <stable@kernel.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Yinghai Lu <yinghai.lu@oracle.com>
[ We'll hopefully find the real fix, but that's too late for 3.1 now ]
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Other than sanity check and debug message, the x86 specific version of
memblock reserve/free functions are simple wrappers around the generic
versions - memblock_reserve/free().

This patch adds debug messages with caller identification to the
generic versions and replaces x86 specific ones and kills them.
arch/x86/include/asm/memblock.h and arch/x86/mm/memblock.c are empty
after this change and removed.
Signed-off-by: NTejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/1310462166-31469-14-git-send-email-tj@kernel.org
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

25818f0f (memblock: Make MEMBLOCK_ERROR be 0) thankfully made
MEMBLOCK_ERROR 0 and there already are codes which expect error return
to be 0.  There's no point in keeping MEMBLOCK_ERROR around.  End its
misery.
Signed-off-by: NTejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/1310457490-3356-6-git-send-email-tj@kernel.org
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Fold all the mmu_gather rework patches into one for submission
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Reported-by: NHugh Dickins <hughd@google.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Miller <davem@davemloft.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Tony Luck <tony.luck@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

With CONFIG_DEBUG_SECTION_MISMATCH=y I see these warnings in next-20110415:

  LD      vmlinux.o
  MODPOST vmlinux.o
WARNING: vmlinux.o(.text+0x1ba48): Section mismatch in reference from the function native_pagetable_reserve() to the function .init.text:memblock_x86_reserve_range()
The function native_pagetable_reserve() references
the function __init memblock_x86_reserve_range().
This is often because native_pagetable_reserve lacks a __init
annotation or the annotation of memblock_x86_reserve_range is wrong.

This patch fixes the issue.
Thanks to pipacs from PaX project for help on IRC.
Acked-by: N"H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: NSedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Introduce a new x86_init hook called pagetable_reserve that at the end
of init_memory_mapping is used to reserve a range of memory addresses for
the kernel pagetable pages we used and free the other ones.

On native it just calls memblock_x86_reserve_range while on xen it also
takes care of setting the spare memory previously allocated
for kernel pagetable pages from RO to RW, so that it can be used for
other purposes.

A detailed explanation of the reason why this hook is needed follows.

As a consequence of the commit:

commit 4b239f45
Author: Yinghai Lu <yinghai@kernel.org>
Date:   Fri Dec 17 16:58:28 2010 -0800

    x86-64, mm: Put early page table high

at some point init_memory_mapping is going to reach the pagetable pages
area and map those pages too (mapping them as normal memory that falls
in the range of addresses passed to init_memory_mapping as argument).
Some of those pages are already pagetable pages (they are in the range
pgt_buf_start-pgt_buf_end) therefore they are going to be mapped RO and
everything is fine.
Some of these pages are not pagetable pages yet (they fall in the range
pgt_buf_end-pgt_buf_top; for example the page at pgt_buf_end) so they
are going to be mapped RW.  When these pages become pagetable pages and
are hooked into the pagetable, xen will find that the guest has already
a RW mapping of them somewhere and fail the operation.
The reason Xen requires pagetables to be RO is that the hypervisor needs
to verify that the pagetables are valid before using them. The validation
operations are called "pinning" (more details in arch/x86/xen/mmu.c).

In order to fix the issue we mark all the pages in the entire range
pgt_buf_start-pgt_buf_top as RO, however when the pagetable allocation
is completed only the range pgt_buf_start-pgt_buf_end is reserved by
init_memory_mapping. Hence the kernel is going to crash as soon as one
of the pages in the range pgt_buf_end-pgt_buf_top is reused (b/c those
ranges are RO).

For this reason we need a hook to reserve the kernel pagetable pages we
used and free the other ones so that they can be reused for other
purposes.
On native it just means calling memblock_x86_reserve_range, on Xen it
also means marking RW the pagetable pages that we allocated before but
that haven't been used before.

Another way to fix this is without using the hook is by adding a 'if
(xen_pv_domain)' in the 'init_memory_mapping' code and calling the Xen
counterpart, but that is just nasty.
Signed-off-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: NYinghai Lu <yinghai@kernel.org>
Acked-by: NH. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

e820_table_{start|end|top}, which are used to buffer page table
allocation during early boot, are now derived from memblock and don't
have much to do with e820.  Change the names so that they reflect what
they're used for.

This patch doesn't introduce any behavior change.

-v2: Ingo found that earlier patch "x86: Use early pre-allocated page
     table buffer top-down" caused crash on 32bit and needed to be
     dropped.  This patch was updated to reflect the change.

-tj: Updated commit description.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NTejun Heo <tj@kernel.org>