Commit Graph

219 Commits

Author SHA1 Message Date
Jens Axboe
8691e5a8f6 smp_call_function: get rid of the unused nonatomic/retry argument
It's never used and the comments refer to nonatomic and retry
interchangably. So get rid of it.

Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-06-26 11:24:35 +02:00
Jens Axboe
c524a1d891 alpha: convert to generic helpers for IPI function calls
This converts alpha to use the new helpers for smp_call_function() and
friends, and adds support for smp_call_function_single().

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-06-26 11:22:57 +02:00
Thorsten Kranzkowski
72c6e251ed alpha: fix compile error in arch/alpha/mm/init.c
Commit 9267b4b388 ("alpha: fix module load
failures on smp (bug #10926)") causes a regression for my ev4
uniprocessor build:

  CC      arch/alpha/mm/init.o
/export/data/repositories/linux-2.6/arch/alpha/mm/init.c:34: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘typeof’
make[2]: *** [arch/alpha/mm/init.o] Error 1
make[1]: *** [arch/alpha/mm] Error 2
make: *** [sub-make] Error 2

This fixes it for me (compile and boot tested):

Signed-off-by: Thorsten Kranzkowski <dl8bcu@dl8bcu.de>
Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-06-23 18:26:04 -07:00
Ivan Kokshaysky
d559d4a24a alpha: fix compile failures with gcc-4.3 (bug #10438)
Vast majority of these build failures are gcc-4.3 warnings
about static functions and objects being referenced from
non-static (read: "extern inline") functions, in conjunction
with our -Werror.

We cannot just convert "extern inline" to "static inline",
as people keep suggesting all the time, because "extern inline"
logic is crucial for generic kernel build.
So
- just make sure that all callees of critical "extern inline"
  functions are also "extern inline";
- use "static inline", wherever it's possible.

traps.c: work around gcc-4.3 being too smart about array
bounds-checking.

TODO: add "gnu_inline" attribute to all our "extern inline"
functions to ensure desired behaviour with future compilers.

Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-06-20 16:46:10 -07:00
Ivan Kokshaysky
9267b4b388 alpha: fix module load failures on smp (bug #10926)
To calculate addresses of locally defined variables, GCC uses 32-bit
displacement from the GP. Which doesn't work for per cpu variables in
modules, as an offset to the kernel per cpu area is way above 4G.

The workaround is to force allocation of a GOT entry for per cpu variable
using ldq instruction with a 'literal' relocation.
I had to use custom asm/percpu.h, as a required argument magic doesn't
work with asm-generic/percpu.h macros.

Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-06-20 16:46:10 -07:00
Mike Frysinger
b7cffc1f29 asm-{alpha,h8300,um,v850,xtensa}/param.h: unbreak HZ for userspace
I noticed this because alpha was broken due to the recent commit commit
bdc807871d ("avoid overflows in
kernel/time.c").  Most arches do something like this in their
asm/param.h:

#ifdef __KERNEL__
# define HZ CONFIG_HZ
#else
# define HZ 100
#endif

A few arches though (namely alpha/h8300/um/v850/xtensa) either do no set
HZ at all for !__KERNEL__, or they set it wrongly.  This should bring all
arches in line by setting up HZ for userspace.

Without this currently perl 5.10 doesn't build on alpha:

perl.c: In function 'perl_construct':
perl.c:388: error: 'CONFIG_HZ' undeclared (first use in this function)
-> http://buildd.debian.org/fetch.cgi?pkg=perl;ver=5.10.0-10;arch=alpha;stamp=1210252894

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: maximilian attems <max@stro.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ HZ on alpha is 1024 for historical reasons.  - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-05-14 19:11:14 -07:00
Nick Piggin
362a61ad61 fix SMP data race in pagetable setup vs walking
There is a possible data race in the page table walking code. After the split
ptlock patches, it actually seems to have been introduced to the core code, but
even before that I think it would have impacted some architectures (powerpc
and sparc64, at least, walk the page tables without taking locks eg. see
find_linux_pte()).

The race is as follows:
The pte page is allocated, zeroed, and its struct page gets its spinlock
initialized. The mm-wide ptl is then taken, and then the pte page is inserted
into the pagetables.

At this point, the spinlock is not guaranteed to have ordered the previous
stores to initialize the pte page with the subsequent store to put it in the
page tables. So another Linux page table walker might be walking down (without
any locks, because we have split-leaf-ptls), and find that new pte we've
inserted. It might try to take the spinlock before the store from the other
CPU initializes it. And subsequently it might read a pte_t out before stores
from the other CPU have cleared the memory.

There are also similar races in higher levels of the page tables. They
obviously don't involve the spinlock, but could see uninitialized memory.

Arch code and hardware pagetable walkers that walk the pagetables without
locks could see similar uninitialized memory problems, regardless of whether
split ptes are enabled or not.

I prefer to put the barriers in core code, because that's where the higher
level logic happens, but the page table accessors are per-arch, and open-coding
them everywhere I don't think is an option. I'll put the read-side barriers
in alpha arch code for now (other architectures perform data-dependent loads
in order).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-05-14 10:05:18 -07:00
Nick Piggin
73f10281ea read_barrier_depends arch fixlets
read_barrie_depends has always been a noop (not a compiler barrier) on all
architectures except SMP alpha. This brings UP alpha and frv into line with all
other architectures, and fixes incorrect documentation.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-05-14 10:05:18 -07:00
Adrian Bunk
36bbfe2f09 fix asm-alpha/types.h breakage
This patch fixes the following compile error on alpha caused by
commit 3726c23df8
(alpha: types: use <asm-generic/int-*.h> for the alpha architecture):

<--  snip  -->

...
  CC      arch/alpha/kernel/asm-offsets.s
In file included from include2/asm/topology.h:6,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/topology.h:34,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/mmzone.h:683,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/gfp.h:4,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/slab.h:12,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/percpu.h:5,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/rcupdate.h:39,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/pid.h:4,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/include/linux/sched.h:74,
                 from /home/bunk/linux/kernel-2.6/git/linux-2.6/arch/alpha/kernel/asm-offsets.c:9:
include2/asm/machvec.h:44: error: expected declaration specifiers or '...' before 'dma_addr_t'
include2/asm/machvec.h:44: error: expected declaration specifiers or '...' before 'dma_addr_t'
In file included from /home/bunk/linux/kernel-2.6/git/linux-2.6/arch/alpha/kernel/asm-offsets.c:12:
include2/asm/io.h:94: warning: type defaults to 'int' in declaration of 'dma_addr_t'
include2/asm/io.h:94: warning: variable 'dma_addr_t' declared 'inline'
include2/asm/io.h:94: error: expected ',' or ';' before 'isa_page_to_bus'
make[2]: *** [arch/alpha/kernel/asm-offsets.s] Error 1

<--  snip  -->

Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2008-05-04 14:45:55 -07:00
H. Peter Anvin
3726c23df8 alpha: types: use <asm-generic/int-*.h> for the alpha architecture
This modifies <asm-alpha/types.h> to use the <asm-generic/int-*.h>
generic include files.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
2008-05-02 16:18:20 -07:00
Harvey Harrison
6510d41954 kernel: Move arches to use common unaligned access
Unaligned access is ok for the following arches:
cris, m68k, mn10300, powerpc, s390, x86

Arches that use the memmove implementation for native endian, and
the byteshifting for the opposite endianness.
h8300, m32r, xtensa

Packed struct for native endian, byteshifting for other endian:
alpha, blackfin, ia64, parisc, sparc, sparc64, mips, sh

m86knommu is generic_be for Coldfire, otherwise unaligned access is ok.

frv, arm chooses endianness based on compiler settings, uses the byteshifting
versions.  Remove the unaligned trap handler from frv as it is now unused.

v850 is le, uses the byteshifting versions for both be and le.

Remove the now unused asm-generic implementation.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-29 08:06:27 -07:00
Andrew Morton
ed6b9b97f4 alpha: teach the compiler that BUG doesn't return
Fix things like this:

security/selinux/netnode.c: In function 'sel_netnode_find':
security/selinux/netnode.c:126: warning: 'idx' may be used uninitialized in this function
security/selinux/netnode.c: In function 'sel_netnode_sid':
security/selinux/netnode.c:225: warning: 'ret' may be used uninitialized in this function
security/selinux/netnode.c:168: warning: 'idx' may be used uninitialized in this function

due to code correctly not expecting BUG() to return.

For some reason this reduces the object code size for that particular file.

Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-28 08:58:27 -07:00
Harvey Harrison
95d193a903 alpha: replace __inline with inline
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-28 08:58:27 -07:00
Nick Piggin
7e675137a8 mm: introduce pte_special pte bit
s390 for one, cannot implement VM_MIXEDMAP with pfn_valid, due to their memory
model (which is more dynamic than most).  Instead, they had proposed to
implement it with an additional path through vm_normal_page(), using a bit in
the pte to determine whether or not the page should be refcounted:

vm_normal_page()
{
	...
        if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
                if (vma->vm_flags & VM_MIXEDMAP) {
#ifdef s390
			if (!mixedmap_refcount_pte(pte))
				return NULL;
#else
                        if (!pfn_valid(pfn))
                                return NULL;
#endif
                        goto out;
                }
	...
}

This is fine, however if we are allowed to use a bit in the pte to determine
refcountedness, we can use that to _completely_ replace all the vma based
schemes.  So instead of adding more cases to the already complex vma-based
scheme, we can have a clearly seperate and simple pte-based scheme (and get
slightly better code generation in the process):

vm_normal_page()
{
#ifdef s390
	if (!mixedmap_refcount_pte(pte))
		return NULL;
	return pte_page(pte);
#else
	...
#endif
}

And finally, we may rather make this concept usable by any architecture rather
than making it s390 only, so implement a new type of pte state for this.
Unfortunately the old vma based code must stay, because some architectures may
not be able to spare pte bits.  This makes vm_normal_page a little bit more
ugly than we would like, but the 2 cases are clearly seperate.

So introduce a pte_special pte state, and use it in mm/memory.c.  It is
currently a noop for all architectures, so this doesn't actually result in any
compiled code changes to mm/memory.o.

BTW:
I haven't put vm_normal_page() into arch code as-per an earlier suggestion.
The reason is that, regardless of where vm_normal_page is actually
implemented, the *abstraction* is still exactly the same. Also, while it
depends on whether the architecture has pte_special or not, that is the
only two possible cases, and it really isn't an arch specific function --
the role of the arch code should be to provide primitive functions and
accessors with which to build the core code; pte_special does that. We do
not want architectures to know or care about vm_normal_page itself, and
we definitely don't want them being able to invent something new there
out of sight of mm/ code. If we made vm_normal_page an arch function, then
we have to make vm_insert_mixed (next patch) an arch function too. So I
don't think moving it to arch code fundamentally improves any abstractions,
while it does practically make the code more difficult to follow, for both
mm and arch developers, and easier to misuse.

[akpm@linux-foundation.org: build fix]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Carsten Otte <cotte@de.ibm.com>
Cc: Jared Hulbert <jaredeh@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-28 08:58:23 -07:00
Alexander van Heukelum
56a6b1eb7b generic: implement __fls on all 64-bit archs
Implement __fls on all 64-bit archs:

alpha has an implementation of fls64.
	Added __fls(x) = fls64(x) - 1.

ia64 has fls, but not __fls.
	Added __fls based on code of fls.

mips and powerpc have __ilog2, which is the same as __fls.
	Added __fls = __ilog2.

parisc, s390, sh and sparc64:
	Include generic __fls.

x86_64 already has __fls.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-04-26 19:21:16 +02:00
Mike Travis
aa6b54461c asm-generic: add node_to_cpumask_ptr macro
Create a simple macro to always return a pointer to the node_to_cpumask(node)
value.  This relies on compiler optimization to remove the extra indirection:

    #define node_to_cpumask_ptr(v, node) 		\
	    cpumask_t _##v = node_to_cpumask(node), *v = &_##v

For those systems with a large cpumask size, then a true pointer
to the array element can be used:

    #define node_to_cpumask_ptr(v, node)		\
	    cpumask_t *v = &(node_to_cpumask_map[node])

A node_to_cpumask_ptr_next() macro is provided to access another
node_to_cpumask value.

The other change is to always include asm-generic/topology.h moving the
ifdef CONFIG_NUMA to this same file.

Note: there are no references to either of these new macros in this patch,
only the definition.

Based on 2.6.25-rc5-mm1

# alpha
Cc: Richard Henderson <rth@twiddle.net>

# fujitsu
Cc: David Howells <dhowells@redhat.com>

# ia64
Cc: Tony Luck <tony.luck@intel.com>

# powerpc
Cc: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>

# sparc
Cc: David S. Miller <davem@davemloft.net>
Cc: William L. Irwin <wli@holomorphy.com>

# x86
Cc: H. Peter Anvin <hpa@zytor.com>

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-04-19 19:44:58 +02:00
Linus Torvalds
188da98800 Merge git://git.kernel.org/pub/scm/linux/kernel/git/bart/ide-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/bart/ide-2.6: (58 commits)
  ide: remove ide_init_default_irq() macro
  ide: move default IDE ports setup to ide_generic host driver
  ide: remove obsoleted "idex=noprobe" kernel parameter (take 2)
  ide: remove needless hwif->irq check from ide_hwif_configure()
  ide: init hwif->{io_ports,irq} explicitly in legacy VLB host drivers
  ide: limit legacy VLB host drivers to alpha, x86 and mips
  cmd640: init hwif->{io_ports,irq} explicitly
  cmd640: cleanup setup_device_ptrs()
  ide: add ide-4drives host driver (take 3)
  ide: remove ppc ifdef from init_ide_data()
  ide: remove ide_default_io_ctl() macro
  ide: remove CONFIG_IDE_ARCH_OBSOLETE_INIT
  ide: add CONFIG_IDE_ARCH_OBSOLETE_DEFAULTS (take 2)
  ppc/pmac: remove no longer needed IDE quirk
  ppc: don't include <linux/ide.h>
  ppc: remove ppc_ide_md
  ppc/pplus: remove ppc_ide_md.ide_init_hwif hook
  ppc/sandpoint: remove ppc_ide_md hooks
  ppc/lopec: remove ppc_ide_md hooks
  ppc/mpc8xx: remove ppc_ide_md hooks
  ...
2008-04-18 08:39:24 -07:00
Bartlomiej Zolnierkiewicz
273b8385e5 ide: remove ide_init_default_irq() macro
* Use ide_default_irq() instead of ide_init_default_irq() in
  ide_generic host driver (so the correct IRQ is always set
  regardless of CONFIG_PCI / CONFIG_BLK_DEV_IDEPCI).

* Remove no longer needed ide_init_default_irq() macro.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
2008-04-18 00:46:35 +02:00
Bartlomiej Zolnierkiewicz
9dfcd15a6d ide: remove ide_default_io_ctl() macro
It is always == '((base) + 0x206)' if CONFIG_IDE_ARCH_OBSOLETE_DEFAULTS=y
and it is not needed otherwise (arm, blackfin, parisc, ppc64, sh, sparc[64]).

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
2008-04-18 00:46:34 +02:00
Bartlomiej Zolnierkiewicz
0e33555fff ide: add CONFIG_IDE_ARCH_OBSOLETE_DEFAULTS (take 2)
* Add CONFIG_IDE_ARCH_OBSOLETE_DEFAULTS to drivers/ide/Kconfig and use
  it instead of defining IDE_ARCH_OBSOLETE_DEFAULTS in <arch/ide.h>.

v2:
* Define ide_default_irq() in ide-probe.c/ns87415.c if not already defined
  and drop defining ide_default_irq() for CONFIG_IDE_ARCH_OBSOLETE_DEFAULTS=n.

  [ Thanks to Stephen Rothwell and David Miller for noticing the problem. ]

Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
2008-04-18 00:46:33 +02:00
Matthew Wilcox
64ac24e738 Generic semaphore implementation
Semaphores are no longer performance-critical, so a generic C
implementation is better for maintainability, debuggability and
extensibility.  Thanks to Peter Zijlstra for fixing the lockdep
warning.  Thanks to Harvey Harrison for pointing out that the
unlikely() was unnecessary.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
2008-04-17 10:42:34 -04:00
Andrew Morton
06f11f37aa alpha: get_current(): don't add zero to current_thread_info()->task
A nasty compile error:

In file included from security/keys/internal.h:16,
                 from security/keys/sysctl.c:14:
include/linux/key-ui.h: In function 'key_permission':
include/linux/key-ui.h:51: error: invalid use of undefined type 'struct task_struct'

apparently the compiler has decided that it needs to know sizeof(task_struct)
so that it can add zero to a task_struct* (which is rather dumb of it).

Getting task_struct in scope in these deeply-nested headers is scary-looking,
so let's just remove the "+ 0".

Cc: David Howells <dhowells@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-02 15:28:20 -07:00
Ivan Kokshaysky
c143d43aa3 alpha: fix ALSA DMA mmap crash
Make dma_alloc_coherent respect gfp flags (__GFP_COMP is one that
matters).

Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Tested-by: Michael Cree <mcree@orcon.net.nz>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-02 15:28:19 -07:00
Christian Borntraeger
dd135ebbd2 kvm: provide kvm.h for all architecture: fixes headers_install
Currently include/linux/kvm.h is not considered by make headers_install,
because Kbuild cannot handle " unifdef-$(CONFIG_FOO) += foo.h.  This problem
was introduced by

commit fb56dbb31c
Author: Avi Kivity <avi@qumranet.com>
Date:   Sun Dec 2 10:50:06 2007 +0200

    KVM: Export include/linux/kvm.h only if $ARCH actually supports KVM

    Currently, make headers_check barfs due to <asm/kvm.h>, which <linux/kvm.h>
    includes, not existing.  Rather than add a zillion <asm/kvm.h>s, export kvm.
    only if the arch actually supports it.

    Signed-off-by: Avi Kivity <avi@qumranet.com>

which makes this an 2.6.25 regression.

One way of solving the issue is to enhance Kbuild, but Avi and David conviced
me, that changing headers_install is not the way to go.  This patch changes
the definition for linux/kvm.h to unifdef-y.

If  unifdef-y is used for linux/kvm.h "make headers_check" will fail on all
architectures without asm/kvm.h.  Therefore, this patch also provides
asm/kvm.h on all architectures.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Avi Kivity <avi@qumranet.com>
Cc: Sam Ravnborg <sam@ravnborg.org
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-02 15:28:18 -07:00
Martin Schwidefsky
2f569afd9c CONFIG_HIGHPTE vs. sub-page page tables.
Background: I've implemented 1K/2K page tables for s390.  These sub-page
page tables are required to properly support the s390 virtualization
instruction with KVM.  The SIE instruction requires that the page tables
have 256 page table entries (pte) followed by 256 page status table entries
(pgste).  The pgstes are only required if the process is using the SIE
instruction.  The pgstes are updated by the hardware and by the hypervisor
for a number of reasons, one of them is dirty and reference bit tracking.
To avoid wasting memory the standard pte table allocation should return
1K/2K (31/64 bit) and 2K/4K if the process is using SIE.

Problem: Page size on s390 is 4K, page table size is 1K or 2K.  That means
the s390 version for pte_alloc_one cannot return a pointer to a struct
page.  Trouble is that with the CONFIG_HIGHPTE feature on x86 pte_alloc_one
cannot return a pointer to a pte either, since that would require more than
32 bit for the return value of pte_alloc_one (and the pte * would not be
accessible since its not kmapped).

Solution: The only solution I found to this dilemma is a new typedef: a
pgtable_t.  For s390 pgtable_t will be a (pte *) - to be introduced with a
later patch.  For everybody else it will be a (struct page *).  The
additional problem with the initialization of the ptl lock and the
NR_PAGETABLE accounting is solved with a constructor pgtable_page_ctor and
a destructor pgtable_page_dtor.  The page table allocation and free
functions need to call these two whenever a page table page is allocated or
freed.  pmd_populate will get a pgtable_t instead of a struct page pointer.
 To get the pgtable_t back from a pmd entry that has been installed with
pmd_populate a new function pmd_pgtable is added.  It replaces the pmd_page
call in free_pte_range and apply_to_pte_range.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:42 -08:00