Now almost all .map_queues() implementation based on managed irq
affinity doesn't update queue mapping and it just retrieves the
old built mapping, so if nr_hw_queues is changed, the mapping talbe
includes stale mapping. And only blk_mq_map_queues() may rebuild
the mapping talbe.

One case is that we limit .nr_hw_queues as 1 in case of kdump kernel.
However, drivers often builds queue mapping before allocating tagset
via pci_alloc_irq_vectors_affinity(), but set->nr_hw_queues can be set
as 1 in case of kdump kernel, so wrong queue mapping is used, and
kernel panic[1] is observed during booting.

This patch fixes the kernel panic triggerd on nvme by rebulding the
mapping table via blk_mq_map_queues().

[1] kernel panic log
[    4.438371] nvme nvme0: 16/0/0 default/read/poll queues
[    4.443277] BUG: unable to handle kernel NULL pointer dereference at 0000000000000098
[    4.444681] PGD 0 P4D 0
[    4.445367] Oops: 0000 [#1] SMP NOPTI
[    4.446342] CPU: 3 PID: 201 Comm: kworker/u33:10 Not tainted 4.20.0-rc5-00664-g5eb02f7ee1eb-dirty #459
[    4.447630] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-2.fc27 04/01/2014
[    4.448689] Workqueue: nvme-wq nvme_scan_work [nvme_core]
[    4.449368] RIP: 0010:blk_mq_map_swqueue+0xfb/0x222
[    4.450596] Code: 04 f5 20 28 ef 81 48 89 c6 39 55 30 76 93 89 d0 48 c1 e0 04 48 03 83 f8 05 00 00 48 8b 00 42 8b 3c 28 48 8b 43 58 48 8b 04 f8 <48> 8b b8 98 00 00 00 4c 0f a3 37 72 42 f0 4c 0f ab 37 66 8b b8 f6
[    4.453132] RSP: 0018:ffffc900023b3cd8 EFLAGS: 00010286
[    4.454061] RAX: 0000000000000000 RBX: ffff888174448000 RCX: 0000000000000001
[    4.456480] RDX: 0000000000000001 RSI: ffffe8feffc506c0 RDI: 0000000000000001
[    4.458750] RBP: ffff88810722d008 R08: ffff88817647a880 R09: 0000000000000002
[    4.464580] R10: ffffc900023b3c10 R11: 0000000000000004 R12: ffff888174448538
[    4.467803] R13: 0000000000000004 R14: 0000000000000001 R15: 0000000000000001
[    4.469220] FS:  0000000000000000(0000) GS:ffff88817bac0000(0000) knlGS:0000000000000000
[    4.471554] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    4.472464] CR2: 0000000000000098 CR3: 0000000174e4e001 CR4: 0000000000760ee0
[    4.474264] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    4.476007] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    4.477061] PKRU: 55555554
[    4.477464] Call Trace:
[    4.478731]  blk_mq_init_allocated_queue+0x36a/0x3ad
[    4.479595]  blk_mq_init_queue+0x32/0x4e
[    4.480178]  nvme_validate_ns+0x98/0x623 [nvme_core]
[    4.480963]  ? nvme_submit_sync_cmd+0x1b/0x20 [nvme_core]
[    4.481685]  ? nvme_identify_ctrl.isra.8+0x70/0xa0 [nvme_core]
[    4.482601]  nvme_scan_work+0x23a/0x29b [nvme_core]
[    4.483269]  ? _raw_spin_unlock_irqrestore+0x25/0x38
[    4.483930]  ? try_to_wake_up+0x38d/0x3b3
[    4.484478]  ? process_one_work+0x179/0x2fc
[    4.485118]  process_one_work+0x1d3/0x2fc
[    4.485655]  ? rescuer_thread+0x2ae/0x2ae
[    4.486196]  worker_thread+0x1e9/0x2be
[    4.486841]  kthread+0x115/0x11d
[    4.487294]  ? kthread_park+0x76/0x76
[    4.487784]  ret_from_fork+0x3a/0x50
[    4.488322] Modules linked in: nvme nvme_core qemu_fw_cfg virtio_scsi ip_tables
[    4.489428] Dumping ftrace buffer:
[    4.489939]    (ftrace buffer empty)
[    4.490492] CR2: 0000000000000098
[    4.491052] ---[ end trace 03cd268ad5a86ff7 ]---

Cc: Christoph Hellwig <hch@lst.de>
Cc: linux-nvme@lists.infradead.org
Cc: David Milburn <dmilburn@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

I was a little overzealous in removing the rcu_read_lock() call from
blkcg_bio_issue_check() and it broke blk-throttle. Put it back.

Fixes: e35403a034bf ("blkcg: associate blkg when associating a device")
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Now that we have this common helper, convert io-latency over to use it
as well.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Now that we have rq_qos_wait() in place, convert wbt_wait() over to
using it with it's specific callbacks.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Originally when I split out the common code from blk-wbt into rq_qos I
left the wbt_wait() where it was and simply copied and modified it
slightly to work for io-latency.  However they are both basically the
same thing, and as time has gone on wbt_wait() has ended up much smarter
and kinder than it was when I copied it into io-latency, which means
io-latency has lost out on these improvements.

Since they are the same thing essentially except for a few minor things,
create rq_qos_wait() that replicates what wbt_wait() currently does with
callbacks that can be passed in for the snowflakes to do their own thing
as appropriate.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

blkg reference counting now uses percpu_ref rather than atomic_t. Let's
make this consistent with css_tryget. This renames blkg_try_get to
blkg_tryget and now returns a bool rather than the blkg or %NULL.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Every bio is now associated with a blkg putting blkg_get, blkg_try_get,
and blkg_put on the hot path. Switch over the refcnt in blkg to use
percpu_ref.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Now that a bio only holds a blkg reference, so clean up is simply
putting back that reference. Remove bio_disassociate_task() as it just
calls bio_disassociate_blkg() and call the latter directly.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The previous patch in this series removed carrying around a pointer to
the css in blkg. However, the blkg association logic still relied on
taking a reference on the css to ensure we wouldn't fail in getting a
reference for the blkg.

Here the implicit dependency on the css is removed. The association
continues to rely on the tryget logic walking up the blkg tree. This
streamlines the three ways that association can happen: normal, swap,
and writeback.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Prior patches ensured that any bio that interacts with a request_queue
is properly associated with a blkg. This makes bio->bi_css unnecessary
as blkg maintains a reference to blkcg already.

This removes the bio field bi_css and transfers corresponding uses to
access via bi_blkg.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

One of the goals of this series is to remove a separate reference to
the css of the bio. This can and should be accessed via bio_blkcg(). In
this patch, wbc_init_bio() now requires a bio to have a device
associated with it.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

A prior patch in this series added blkg association to bios issued by
cgroups. There are two other paths that we want to attribute work back
to the appropriate cgroup: swap and writeback. Here we modify the way
swap tags bios to include the blkg. Writeback will be tackle in the next
patch.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

bio_issue_init among other things initializes the timestamp for an IO.
Rather than have this logic handled by policies, this consolidates it to
be on the init paths (normal, clone, bounce clone).
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Previously, blkg association was handled by controller specific code in
blk-throttle and blk-iolatency. However, because a blkg represents a
relationship between a blkcg and a request_queue, it makes sense to keep
the blkg->q and bio->bi_disk->queue consistent.

This patch moves association into the bio_set_dev macro(). This should
cover the majority of cases where the device is set/changed keeping the
two pointers consistent. Fallback code is added to
blkcg_bio_issue_check() to catch any missing paths.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The next patch changes the macro bio_set_dev() to associate a bio with a
blkg based on the device set. However, dm creates a static bio to be
used as the basis for cloning empty flush bios on creation. The
bio_set_dev() call in alloc_dev() will cause problems with the next
patch adding association to bio_set_dev() because the call is before the
bdev is associated with a gendisk (bd_disk is %NULL). To get around
this, set the device on the static bio every time and use that to clone
to the other bios.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

There are 3 ways blkg association can happen: association with the
current css, with the page css (swap), or from the wbc css (writeback).

This patch handles how association is done for the first case where we
are associating bsaed on the current css. If there is already a blkg
associated, the css will be reused and association will be redone as the
request_queue may have changed.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

There are several scenarios where blkg_lookup_create() can fail such as
the blkcg dying, request_queue is dying, or simply being OOM. Most
handle this by simply falling back to the q->root_blkg and calling it a
day.

This patch implements the notion of closest blkg. During
blkg_lookup_create(), if it fails to create, return the closest blkg
found or the q->root_blkg. blkg_try_get_closest() is introduced and used
during association so a bio is always attached to a blkg.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

To know when to create a blkg, the general pattern is to do a
blkg_lookup() and if that fails, lock and do the lookup again, and if
that fails finally create. It doesn't make much sense for everyone who
wants to do creation to write this themselves.

This changes blkg_lookup_create() to do locking and implement this
pattern. The old blkg_lookup_create() is renamed to
__blkg_lookup_create().  If a call site wants to do its own error
handling or already owns the queue lock, they can use
__blkg_lookup_create(). This will be used in upcoming patches.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The bio_blkcg() function turns out to be inconsistent and consequently
dangerous to use. The first part returns a blkcg where a reference is
owned by the bio meaning it does not need to be rcu protected. However,
the third case, the last line, is problematic:

	return css_to_blkcg(task_css(current, io_cgrp_id));

This can race against task migration and the cgroup dying. It is also
semantically different as it must be called rcu protected and is
susceptible to failure when trying to get a reference to it.

This patch adds association ahead of calling bio_blkcg() rather than
after. This makes association a required and explicit step along the
code paths for calling bio_blkcg(). In blk-iolatency, association is
moved above the bio_blkcg() call to ensure it will not return %NULL.

BFQ uses the old bio_blkcg() function, but I do not want to address it
in this series due to the complexity. I have created a private version
documenting the inconsistency and noting not to use it.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We only support polling if we have poll queues now, but the flag is
being set by default. Remove the default QUEUE_FLAG_POLL setting, we'll
set it in blk_mq_init_allocated_queue() if we have poll queues available
for this device.

Fixes: 6544d229 ("block: enable polling by default if a poll map is initalized")
Reported-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

If the user did setup polling in the driver we should not require
another know in the block layer to enable it.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This avoids having to have differnet mq_ops for different setups
with or without poll queues.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This was intended to support users like nvme multipath, but is just
getting in the way and adding another indirect call.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The ->poll_fn has been stale for a while, as a lot of places check for mq
ops.  But there is no real point in it anyway, as we don't even use
the multipath code for subsystems without multiple ports, which is usually
what we do high performance I/O to.  If it really becomes an issue we
should rework the nvme code to also skip the multipath code for any
private namespace, even if that could mean some trouble when rescanning.
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The code was always a bit of a hack that digs far too much into
RDMA core internals.  Lets kick it out and reimplement proper
dedicated poll queues as needed.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Now that we can't poll regular, interrupt driven I/O queues there
is almost nothing that can race with an interrupt.  The only
possible other contexts polling a CQ are the error handler and
queue shutdown, and both are so far off in the slow path that
we can simply use the big hammer of disabling interrupts.

With that we can stop taking the cq_lock for normal queues.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This is the last place outside of nvme_irq that handles CQEs from
interrupt context, and thus is in the way of removing the cq_lock for
normal queues, and avoiding lockdep warnings on the poll queues, for
which we already take it without IRQ disabling.
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pass the opcode for the delete SQ/CQ command as an argument instead of
the somewhat confusing pass loop.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We have three places that can poll for I/O completions on a normal
interrupt-enabled queue.  All of them are in slow path code, so
consolidate them to a single helper that uses spin_lock_irqsave and
removes the fast path cqe_pending check.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This will allow us to simplify both the regular NVMe interrupt handler
and the upcoming aio poll code.  In addition to that the separate
queues are generally a good idea for performance reasons.
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Use a bit flag to mark if the SQ was allocated from the CMB, and clean
up the surrounding code a bit.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This gets rid of all the messing with cq_vector and the ->polled field
by using an atomic bitop to mark the queue enabled or not.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Having another indirect all in the fast path doesn't really help
in our post-spectre world.  Also having too many queue type is just
going to create confusion, so I'd rather manage them centrally.

Note that the queue type naming and ordering changes a bit - the
first index now is the default queue for everything not explicitly
marked, the optional ones are read and poll queues.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

No one is going to poll for aio (yet), so we must clear the HIPRI
flag, as we would otherwise send it down the poll queues, where no
one will be polling for completions.
Signed-off-by: Christoph Hellwig <hch@lst.de>

IOCB_HIPRI, not RWF_HIPRI.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull in v4.20-rc5, solving a conflict we'll otherwise get in aio.c and
also getting the merge fix that went into mainline that users are
hitting testing for-4.21/block and/or for-next.

* tag 'v4.20-rc5': (664 commits)
  Linux 4.20-rc5
  PCI: Fix incorrect value returned from pcie_get_speed_cap()
  MAINTAINERS: Update linux-mips mailing list address
  ocfs2: fix potential use after free
  mm/khugepaged: fix the xas_create_range() error path
  mm/khugepaged: collapse_shmem() do not crash on Compound
  mm/khugepaged: collapse_shmem() without freezing new_page
  mm/khugepaged: minor reorderings in collapse_shmem()
  mm/khugepaged: collapse_shmem() remember to clear holes
  mm/khugepaged: fix crashes due to misaccounted holes
  mm/khugepaged: collapse_shmem() stop if punched or truncated
  mm/huge_memory: fix lockdep complaint on 32-bit i_size_read()
  mm/huge_memory: splitting set mapping+index before unfreeze
  mm/huge_memory: rename freeze_page() to unmap_page()
  initramfs: clean old path before creating a hardlink
  kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc() as notrace
  psi: make disabling/enabling easier for vendor kernels
  proc: fixup map_files test on arm
  debugobjects: avoid recursive calls with kmemleak
  userfaultfd: shmem: UFFDIO_COPY: set the page dirty if VM_WRITE is not set
  ...

We need to ignore bits in the cleared mask when iterating over all set
bits.

Fixes: ea86ea2c ("sbitmap: ammortize cost of clearing bits")
Reported-by: Jens Axboe@kernel.dk>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We only need the request fields and the end_io time if we have
stats enabled, or if we have a scheduler attached as those may
use it for completion time stats.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull ARM SoC fixes from Olof Johansson:
 "Volume is a little higher than usual due to a set of gpio fixes for
  Davinci platforms that's been around a while, still seemed appropriate
  to not hold off until next merge window.

  Besides that it's the usual mix of minor fixes, mostly corrections of
  small stuff in device trees.

  Major stability-related one is the removal of a regulator from DT on
  Rock960, since DVFS caused undervoltage. I expect it'll be restored
  once they figure out the underlying issue"

* tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (28 commits)
  MAINTAINERS: Remove unused Qualcomm SoC mailing list
  ARM: davinci: dm644x: set the GPIO base to 0
  ARM: davinci: da830: set the GPIO base to 0
  ARM: davinci: dm355: set the GPIO base to 0
  ARM: davinci: dm646x: set the GPIO base to 0
  ARM: davinci: dm365: set the GPIO base to 0
  ARM: davinci: da850: set the GPIO base to 0
  gpio: davinci: restore a way to manually specify the GPIO base
  ARM: davinci: dm644x: define gpio interrupts as separate resources
  ARM: davinci: dm355: define gpio interrupts as separate resources
  ARM: davinci: dm646x: define gpio interrupts as separate resources
  ARM: davinci: dm365: define gpio interrupts as separate resources
  ARM: davinci: da8xx: define gpio interrupts as separate resources
  ARM: dts: at91: sama5d2: use the divided clock for SMC
  ARM: dts: imx51-zii-rdu1: Remove EEPROM node
  ARM: dts: rockchip: Remove @0 from the veyron memory node
  arm64: dts: rockchip: Fix PCIe reset polarity for rk3399-puma-haikou.
  arm64: dts: qcom: msm8998: Reserve gpio ranges on MTP
  arm64: dts: sdm845-mtp: Reserve reserved gpios
  arm64: dts: ti: k3-am654: Fix wakeup_uart reg address
  ...

Pull xen fixes from Juergen Gross:

 - A revert of a previous commit as it is no longer necessary and has
   shown to cause problems in some memory hotplug cases.

 - Some small fixes and a minor cleanup.

 - A patch for adding better diagnostic data in a very rare failure
   case.

* tag 'for-linus-4.20a-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  pvcalls-front: fixes incorrect error handling
  Revert "xen/balloon: Mark unallocated host memory as UNUSABLE"
  xen: xlate_mmu: add missing header to fix 'W=1' warning
  xen/x86: add diagnostic printout to xen_mc_flush() in case of error
  x86/xen: cleanup includes in arch/x86/xen/spinlock.c