I think we may have a race between try_to_wake_up() and
migrate_live_tasks() -> move_task_off_dead_cpu() when the later one
may end up looping endlessly.

Interrupts are enabled on other CPUs when migration_call(CPU_DEAD, ...) is
called so we may get a race between try_to_wake_up() and
migrate_live_tasks() -> move_task_off_dead_cpu(). The former one may push
a task out of a dead CPU causing the later one to loop endlessly.

Heiko Carstens observed:

| That's exactly what explains a dump I got yesterday. Thanks for fixing! :)
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Cc: miaox@cn.fujitsu.com
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Avi Kivity <avi@qumranet.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Here it is another little Oops we found while configuring invalid values
via cgroups:

echo 0 > /dev/cgroups/0/cpu.rt_period_us
or
echo 4294967296 > /dev/cgroups/0/cpu.rt_period_us

[  205.509825] divide error: 0000 [#1]
[  205.510151] Modules linked in:
[  205.510151]
[  205.510151] Pid: 2339, comm: bash Not tainted (2.6.26-rc8 #33)
[  205.510151] EIP: 0060:[<c030c6ef>] EFLAGS: 00000293 CPU: 0
[  205.510151] EIP is at div64_u64+0x5f/0x70
[  205.510151] EAX: 0000389f EBX: 00000000 ECX: 00000000 EDX: 00000000
[  205.510151] ESI: d9800000 EDI: 00000000 EBP: c6cede60 ESP: c6cede50
[  205.510151]  DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
[  205.510151] Process bash (pid: 2339, ti=c6cec000 task=c79be370 task.ti=c6cec000)
[  205.510151] Stack: d9800000 0000389f c05971a0 d9800000 c6cedeb4 c0214dbd 00000000 00000000
[  205.510151]        c6cede88 c0242bd8 c05377c0 c7a41b40 00000000 00000000 00000000 c05971a0
[  205.510151]        c780ed20 c7508494 c7a41b40 00000000 00000002 c6cedebc c05971a0 ffffffea
[  205.510151] Call Trace:
[  205.510151]  [<c0214dbd>] ? __rt_schedulable+0x1cd/0x240
[  205.510151]  [<c0242bd8>] ? cgroup_file_open+0x18/0xe0
[  205.510151]  [<c0214fe4>] ? tg_set_bandwidth+0xa4/0xf0
[  205.510151]  [<c0215066>] ? sched_group_set_rt_period+0x36/0x50
[  205.510151]  [<c021508e>] ? cpu_rt_period_write_uint+0xe/0x10
[  205.510151]  [<c0242dc5>] ? cgroup_file_write+0x125/0x160
[  205.510151]  [<c0232c15>] ? hrtimer_interrupt+0x155/0x190
[  205.510151]  [<c02f047f>] ? security_file_permission+0xf/0x20
[  205.510151]  [<c0277ad8>] ? rw_verify_area+0x48/0xc0
[  205.510151]  [<c0283744>] ? dupfd+0x104/0x130
[  205.510151]  [<c027838c>] ? vfs_write+0x9c/0x160
[  205.510151]  [<c0242ca0>] ? cgroup_file_write+0x0/0x160
[  205.510151]  [<c027850d>] ? sys_write+0x3d/0x70
[  205.510151]  [<c0203019>] ? sysenter_past_esp+0x6a/0x91
[  205.510151]  =======================
[  205.510151] Code: 0f 45 de 31 f6 0f ad d0 d3 ea f6 c1 20 0f 45 c2 0f 45 d6 89 45 f0 89 55 f4 8b 55 f4 31 c9 8b 45 f0 39 d3 89 c6 77 08 89 d0 31 d2 <f7> f3 89 c1 83 c4 08 89 f0 f7 f3 89 ca 5b 5e 5d c3 55 89 e5 56
[  205.510151] EIP: [<c030c6ef>] div64_u64+0x5f/0x70 SS:ESP 0068:c6cede50

The attached patch solves the issue for me.

I'm checking as soon as possible for the period not being zero since, if
it is, going ahead is useless. This way we also save a mutex_lock() and
a read_lock() wrt doing it inside tg_set_bandwidth() or
__rt_schedulable().
Signed-off-by: Dario Faggioli <raistlin@linux.it>
Signed-off-by: Michael Trimarchi <trimarchimichael@yahoo.it>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

the CPU hotplug problems (crashes under high-volume unplug+replug
tests) seem to be related to migrate_dead_tasks().

Firstly I added traces to see all tasks being migrated with
migrate_live_tasks() and migrate_dead_tasks(). On my setup the problem
pops up (the one with "se == NULL" in the loop of
pick_next_task_fair()) shortly after the traces indicate that some has
been migrated with migrate_dead_tasks()). btw., I can reproduce it
much faster now with just a plain cpu down/up loop.

[disclaimer] Well, unless I'm really missing something important in
this late hour [/desclaimer] pick_next_task() is not something
appropriate for migrate_dead_tasks() :-)

the following change seems to eliminate the problem on my setup
(although, I kept it running only for a few minutes to get a few
messages indicating migrate_dead_tasks() does move tasks and the
system is still ok)
Signed-off-by: Ingo Molnar <mingo@elte.hu>

* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6:
  [IA64] Eliminate NULL test after alloc_bootmem in iosapic_alloc_rte()
  [IA64] Handle count==0 in sn2_ptc_proc_write()
  [IA64] Fix boot failure on ia64/sn2

* git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-2.6-fixes:
  [GFS2] fix gfs2 block allocation (cleaned up)
  [GFS2] BUG: unable to handle kernel paging request at ffff81002690e000

* 'kvm-updates-2.6.26' of git://git.kernel.org/pub/scm/linux/kernel/git/avi/kvm:
  KVM: Remove now unused structs from kvm_para.h
  x86: KVM guest: Use the paravirt clocksource structs and functions
  KVM: Make kvm host use the paravirt clocksource structs
  x86: Make xen use the paravirt clocksource structs and functions
  x86: Add structs and functions for paravirt clocksource
  KVM: VMX: Fix host msr corruption with preemption enabled
  KVM: ioapic: fix lost interrupt when changing a device's irq
  KVM: MMU: Fix oops on guest userspace access to guest pagetable
  KVM: MMU: large page update_pte issue with non-PAE 32-bit guests (resend)
  KVM: MMU: Fix rmap_write_protect() hugepage iteration bug
  KVM: close timer injection race window in __vcpu_run
  KVM: Fix race between timer migration and vcpu migration

* git://git.kernel.org/pub/scm/linux/kernel/git/wim/linux-2.6-watchdog:
  Revert "[WATCHDOG] hpwdt: Add CFLAGS to get driver working"

Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  xen: remove support for non-PAE 32-bit

* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb:
  kgdb: sparse fix
  kgdb: documentation update - remove kgdboe

On 9xx chips, bus mastering needs to be enabled at resume time for much of the
chip to function.  With this patch, vblank interrupts will work as expected
on resume, along with other chip functions.   Fixes kernel bugzilla #10844.
Signed-off-by: Jie Luo <clotho67@gmail.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The kvm_* structs are obsoleted by the pvclock_* ones.
Now all users have been switched over and the old structs
can be dropped.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

This patch updates the kvm host code to use the pvclock structs
and functions, thereby making it compatible with Xen.

The patch also fixes an initialization bug: on SMP systems the
per-cpu has two different locations early at boot and after CPU
bringup.  kvmclock must take that in account when registering the
physical address within the host.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

This patch updates the kvm host code to use the pvclock structs.
It also makes the paravirt clock compatible with Xen.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

This patch updates the xen guest to use the pvclock structs
and helper functions.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

This patch adds structs for the paravirt clocksource ABI
used by both xen and kvm (pvclock-abi.h).

It also adds some helper functions to read system time and
wall clock time from a paravirtual clocksource (pvclock.[ch]).
They are based on the xen code.  They are enabled using
CONFIG_PARAVIRT_CLOCK.

Subsequent patches of this series will put the code in use.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

This patch fixes bz 450641.

This patch changes the computation for zero_metapath_length(), which it
renames to metapath_branch_start(). When you are extending the metadata
tree, The indirect blocks that point to the new data block must either
diverge from the existing tree either at the inode, or at the first
indirect block. They can diverge at the first indirect block because the
inode has room for 483 pointers while the indirect blocks have room for
509 pointers, so when the tree is grown, there is some free space in the
first indirect block. What metapath_branch_start() now computes is the
height where the first indirect block for the new data block is located.
It can either be 1 (if the indirect block diverges from the inode) or 2
(if it diverges from the first indirect block).
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

As noted by Akinobu Mita alloc_bootmem and related functions never return
NULL and always return a zeroed region of memory.  Thus a NULL test or
memset after calls to these functions is unnecessary.
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Tony Luck <tony.luck@intel.com>

The fix applied in e0c6d97c
"security hole in sn2_ptc_proc_write" didn't take into account
the case where count==0 (which results in a buffer underrun
when adding the trailing '\0').  Thanks to Andi Kleen for
pointing this out.
Signed-off-by: Cliff Wickman <cpw@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

Call check_sal_cache_flush() after platform_setup() as
check_sal_cache_flush() now relies on being able to call platform
vector code.

Problem was introduced by: 3463a93d
"Update check_sal_cache_flush to use platform_send_ipi()"
Signed-off-by: Jes Sorensen <jes@sgi.com>
Tested-by: Alex Chiang: <achiang@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

- Fix warning reported by sparse
kernel/kgdb.c:1502:6: warning: symbol 'kgdb_console_write' was not declared.
	Should it be static?
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

kgdboe is not presently included kgdb, and there should be no
references to it.

Also fix the tcp port terminal connection example.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

Non-PAE operation has been deprecated in Xen for a while, and is
rarely tested or used.  xen-unstable has now officially dropped
non-PAE support.  Since Xen/pvops' non-PAE support has also been
broken for a while, we may as well completely drop it altogether.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

This patch fixes bugzilla bug bz448866: gfs2: BUG: unable to
handle kernel paging request at ffff81002690e000.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

After Linus fixed the inline assembly, the CFLAGS option is not
needed anymore.
Signed-off-by: Thomas Mingarelli <Thomas.Mingarelli@hp.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

Switching msrs can occur either synchronously as a result of calls to
the msr management functions (usually in response to the guest touching
virtualized msrs), or asynchronously when preempting a kvm thread that has
guest state loaded.  If we're unlucky enough to have the two at the same
time, host msrs are corrupted and the machine goes kaput on the next syscall.

Most easily triggered by Windows Server 2008, as it does a lot of msr
switching during bootup.
Signed-off-by: Avi Kivity <avi@qumranet.com>

The ioapic acknowledge path translates interrupt vectors to irqs.  It
currently uses a first match algorithm, stopping when it finds the first
redirection table entry containing the vector.  That fails however if the
guest changes the irq to a different line, leaving the old redirection table
entry in place (though masked).  Result is interrupts not making it to the
guest.

Fix by always scanning the entire redirection table.
Signed-off-by: Avi Kivity <avi@qumranet.com>

KVM has a heuristic to unshadow guest pagetables when userspace accesses
them, on the assumption that most guests do not allow userspace to access
pagetables directly. Unfortunately, in addition to unshadowing the pagetables,
it also oopses.

This never triggers on ordinary guests since sane OSes will clear the
pagetables before assigning them to userspace, which will trigger the flood
heuristic, unshadowing the pagetables before the first userspace access. One
particular guest, though (Xenner) will run the kernel in userspace, triggering
the oops.  Since the heuristic is incorrect in this case, we can simply
remove it.
Signed-off-by: Avi Kivity <avi@qumranet.com>

kvm_mmu_pte_write() does not handle 32-bit non-PAE large page backed
guests properly. It will instantiate two 2MB sptes pointing to the same
physical 2MB page when a guest large pte update is trapped.

Instead of duplicating code to handle this, disallow directory level
updates to happen through kvm_mmu_pte_write(), so the two 2MB sptes
emulating one guest 4MB pte can be correctly created by the page fault
handling path.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

rmap_next() does not work correctly after rmap_remove(), as it expects
the rmap chains not to change during iteration.  Fix (for now) by restarting
iteration from the beginning.
Signed-off-by: Avi Kivity <avi@qumranet.com>

If a timer fires after kvm_inject_pending_timer_irqs() but before
local_irq_disable() the code will enter guest mode and only inject such
timer interrupt the next time an unrelated event causes an exit.

It would be simpler if the timer->pending irq conversion could be done
with IRQ's disabled, so that the above problem cannot happen.

For now introduce a new vcpu requests bit to cancel guest entry.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

A guest vcpu instance can be scheduled to a different physical CPU
between the test for KVM_REQ_MIGRATE_TIMER and local_irq_disable().

If that happens, the timer will only be migrated to the current pCPU on
the next exit, meaning that guest LAPIC timer event can be delayed until
a host interrupt is triggered.

Fix it by cancelling guest entry if any vcpu request is pending.  This
has the side effect of nicely consolidating vcpu->requests checks.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

Commit 9267b4b3 ("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>

* 'hotfixes' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6:
  NFS: nfs_updatepage(): don't mark page as dirty if an error occurred
  NFS: Fix filehandle size comparisons in the mount code
  NFS: Reduce the NFS mount code stack usage.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

Fix a sign issue in xdr_decode_fhstatus3()
Fix incorrect comparison in nfs_validate_mount_data()
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

This appears to fix the Oops reported in
  http://bugzilla.kernel.org/show_bug.cgi?id=10826Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  futexes: fix fault handling in futex_lock_pi

Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: refactor wait_for_completion_timeout()
  sched: fix wait_for_completion_timeout() spurious failure under heavy load
  sched: rt: dont stop the period timer when there are tasks wanting to run

Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  xen: don't drop NX bit
  xen: mask unwanted pte bits in __supported_pte_mask
  xen: Use wmb instead of rmb in xen_evtchn_do_upcall().
  x86: fix NULL pointer deref in __switch_to