[ Upstream commit 88ca2521bd5b4e8b83743c01a2d4cb09325b51e9 ]
There is a TOCTOU issue in set_evtchn_to_irq. Rows in the evtchn_to_irq
mapping are lazily allocated in this function. The check whether the row
is already present and the row initialization is not synchronized. Two
threads can at the same time allocate a new row for evtchn_to_irq and
add the irq mapping to the their newly allocated row. One thread will
overwrite what the other has set for evtchn_to_irq[row] and therefore
the irq mapping is lost. This will trigger a BUG_ON later in
bind_evtchn_to_cpu:
INFO: pci 0000:1a:15.4: [1d0f:8061] type 00 class 0x010802
INFO: nvme 0000:1a:12.1: enabling device (0000 -> 0002)
INFO: nvme nvme77: 1/0/0 default/read/poll queues
CRIT: kernel BUG at drivers/xen/events/events_base.c:427!
WARN: invalid opcode: 0000 [#1] SMP NOPTI
WARN: Workqueue: nvme-reset-wq nvme_reset_work [nvme]
WARN: RIP: e030:bind_evtchn_to_cpu+0xc2/0xd0
WARN: Call Trace:
WARN: set_affinity_irq+0x121/0x150
WARN: irq_do_set_affinity+0x37/0xe0
WARN: irq_setup_affinity+0xf6/0x170
WARN: irq_startup+0x64/0xe0
WARN: __setup_irq+0x69e/0x740
WARN: ? request_threaded_irq+0xad/0x160
WARN: request_threaded_irq+0xf5/0x160
WARN: ? nvme_timeout+0x2f0/0x2f0 [nvme]
WARN: pci_request_irq+0xa9/0xf0
WARN: ? pci_alloc_irq_vectors_affinity+0xbb/0x130
WARN: queue_request_irq+0x4c/0x70 [nvme]
WARN: nvme_reset_work+0x82d/0x1550 [nvme]
WARN: ? check_preempt_wakeup+0x14f/0x230
WARN: ? check_preempt_curr+0x29/0x80
WARN: ? nvme_irq_check+0x30/0x30 [nvme]
WARN: process_one_work+0x18e/0x3c0
WARN: worker_thread+0x30/0x3a0
WARN: ? process_one_work+0x3c0/0x3c0
WARN: kthread+0x113/0x130
WARN: ? kthread_park+0x90/0x90
WARN: ret_from_fork+0x3a/0x50
This patch sets evtchn_to_irq rows via a cmpxchg operation so that they
will be set only once. The row is now cleared before writing it to
evtchn_to_irq in order to not create a race once the row is visible for
other threads.
While at it, do not require the page to be zeroed, because it will be
overwritten with -1's in clear_evtchn_to_irq_row anyway.
Signed-off-by: Maximilian Heyne <mheyne@amazon.de>
Fixes: d0b075ffee ("xen/events: Refactor evtchn_to_irq array to be dynamically allocated")
Link: https://lore.kernel.org/r/20210812130930.127134-1-mheyne@amazon.de
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 3de218ff39b9e3f0d453fe3154f12a174de44b25 upstream.
In order to avoid a race condition for user events when changing
cpu affinity reset the active flag only when EOI-ing the event.
This is working fine as all user events are lateeoi events. Note that
lateeoi_ack_mask_dynirq() is not modified as there is no explicit call
to xen_irq_lateeoi() expected later.
Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Fixes: b6622798bc50b62 ("xen/events: avoid handling the same event on two cpus at the same time")
Tested-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrvsky@oracle.com>
Link: https://lore.kernel.org/r/20210623130913.9405-1-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The backport of upstream patch 25da4618af240fbec61 ("xen/events: don't
unmask an event channel when an eoi is pending") introduced a
regression for stable kernels 5.10 and older: setting IRQ affinity for
IRQs related to interdomain events would no longer work, as moving the
IRQ to its new cpu was not included in the irq_ack callback for those
events.
Fix that by adding the needed call.
Note that kernels 5.11 and later don't need the explicit moving of the
IRQ to the target cpu in the irq_ack callback, due to a rework of the
affinity setting in kernel 5.11.
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit d120198bd5ff1d41808b6914e1eb89aff937415c upstream.
Unmask operation must be called with interrupt disabled,
on preempt_rt spin_lock_irqsave/spin_unlock_irqrestore
don't disable/enable interrupts, so use raw_* implementation
and change lock variable in struct irq_info from spinlock_t
to raw_spinlock_t
Cc: stable@vger.kernel.org
Fixes: 25da4618af24 ("xen/events: don't unmask an event channel when an eoi is pending")
Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Wei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/20210406105105.10141-1-luca.fancellu@arm.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit b6622798bc50b625a1e62f82c7190df40c1f5b21 upstream.
When changing the cpu affinity of an event it can happen today that
(with some unlucky timing) the same event will be handled on the old
and the new cpu at the same time.
Avoid that by adding an "event active" flag to the per-event data and
call the handler only if this flag isn't set.
Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Link: https://lore.kernel.org/r/20210306161833.4552-4-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 25da4618af240fbec6112401498301a6f2bc9702 upstream.
An event channel should be kept masked when an eoi is pending for it.
When being migrated to another cpu it might be unmasked, though.
In order to avoid this keep three different flags for each event channel
to be able to distinguish "normal" masking/unmasking from eoi related
masking/unmasking and temporary masking. The event channel should only
be able to generate an interrupt if all flags are cleared.
Cc: stable@vger.kernel.org
Fixes: 54c9de89895e ("xen/events: add a new "late EOI" evtchn framework")
Reported-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Tested-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Link: https://lore.kernel.org/r/20210306161833.4552-3-jgross@suse.com
[boris -- corrected Fixed tag format]
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 9e77d96b8e2724ed00380189f7b0ded61113b39f upstream.
When creating a new event channel with 2-level events the affinity
needs to be reset initially in order to avoid using an old affinity
from earlier usage of the event channel port. So when tearing an event
channel down reset all affinity bits.
The same applies to the affinity when onlining a vcpu: all old
affinity settings for this vcpu must be reset. As percpu events get
initialized before the percpu event channel hook is called,
resetting of the affinities happens after offlining a vcpu (this is
working, as initial percpu memory is zeroed out).
Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Link: https://lore.kernel.org/r/20210306161833.4552-2-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 3499ba8198cad47b731792e5e56b9ec2a78a83a2 ]
For a while, event channel notification via the PCI platform device
has been broken, because we attempt to communicate with xenstore before
we even have notifications working, with the xs_reset_watches() call
in xs_init().
We tend to get away with this on Xen versions below 4.0 because we avoid
calling xs_reset_watches() anyway, because xenstore might not cope with
reading a non-existent key. And newer Xen *does* have the vector
callback support, so we rarely fall back to INTX/GSI delivery.
To fix it, clean up a bit of the mess of xs_init() and xenbus_probe()
startup. Call xs_init() directly from xenbus_init() only in the !XS_HVM
case, deferring it to be called from xenbus_probe() in the XS_HVM case
instead.
Then fix up the invocation of xenbus_probe() to happen either from its
device_initcall if the callback is available early enough, or when the
callback is finally set up. This means that the hack of calling
xenbus_probe() from a workqueue after the first interrupt, or directly
from the PCI platform device setup, is no longer needed.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20210113132606.422794-2-dwmw2@infradead.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 5f7f77400ab5b357b5fdb7122c3442239672186c upstream.
In order to avoid high dom0 load due to rogue guests sending events at
high frequency, block those events in case there was no action needed
in dom0 to handle the events.
This is done by adding a per-event counter, which set to zero in case
an EOI without the XEN_EOI_FLAG_SPURIOUS is received from a backend
driver, and incremented when this flag has been set. In case the
counter is 2 or higher delay the EOI by 1 << (cnt - 2) jiffies, but
not more than 1 second.
In order not to waste memory shorten the per-event refcnt to two bytes
(it should normally never exceed a value of 2). Add an overflow check
to evtchn_get() to make sure the 2 bytes really won't overflow.
This is part of XSA-332.
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Wei Liu <wl@xen.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit e99502f76271d6bc4e374fe368c50c67a1fd3070 upstream.
In case rogue guests are sending events at high frequency it might
happen that xen_evtchn_do_upcall() won't stop processing events in
dom0. As this is done in irq handling a crash might be the result.
In order to avoid that, delay further inter-domain events after some
time in xen_evtchn_do_upcall() by forcing eoi processing into a
worker on the same cpu, thus inhibiting new events coming in.
The time after which eoi processing is to be delayed is configurable
via a new module parameter "event_loop_timeout" which specifies the
maximum event loop time in jiffies (default: 2, the value was chosen
after some tests showing that a value of 2 was the lowest with an
only slight drop of dom0 network throughput while multiple guests
performed an event storm).
How long eoi processing will be delayed can be specified via another
parameter "event_eoi_delay" (again in jiffies, default 10, again the
value was chosen after testing with different delay values).
This is part of XSA-332.
Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Wei Liu <wl@xen.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 7beb290caa2adb0a399e735a1e175db9aae0523a upstream.
Today only fifo event channels have a cpu hotplug callback. In order
to prepare for more percpu (de)init work move that callback into
events_base.c and add percpu_init() and percpu_deinit() hooks to
struct evtchn_ops.
This is part of XSA-332.
Cc: stable@vger.kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wl@xen.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 54c9de89895e0a36047fcc4ae754ea5b8655fb9d upstream.
In order to avoid tight event channel related IRQ loops add a new
framework of "late EOI" handling: the IRQ the event channel is bound
to will be masked until the event has been handled and the related
driver is capable to handle another event. The driver is responsible
for unmasking the event channel via the new function xen_irq_lateeoi().
This is similar to binding an event channel to a threaded IRQ, but
without having to structure the driver accordingly.
In order to support a future special handling in case a rogue guest
is sending lots of unsolicited events, add a flag to xen_irq_lateeoi()
which can be set by the caller to indicate the event was a spurious
one.
This is part of XSA-332.
Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Wei Liu <wl@xen.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 073d0552ead5bfc7a3a9c01de590e924f11b5dd2 upstream.
Today it can happen that an event channel is being removed from the
system while the event handling loop is active. This can lead to a
race resulting in crashes or WARN() splats when trying to access the
irq_info structure related to the event channel.
Fix this problem by using a rwlock taken as reader in the event
handling loop and as writer when deallocating the irq_info structure.
As the observed problem was a NULL dereference in evtchn_from_irq()
make this function more robust against races by testing the irq_info
pointer to be not NULL before dereferencing it.
And finally make all accesses to evtchn_to_irq[row][col] atomic ones
in order to avoid seeing partial updates of an array element in irq
handling. Note that irq handling can be entered only for event channels
which have been valid before, so any not populated row isn't a problem
in this regard, as rows are only ever added and never removed.
This is XSA-331.
Cc: stable@vger.kernel.org
Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reported-by: Jinoh Kang <luke1337@theori.io>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Wei Liu <wl@xen.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 0891fb39ba67bd7ae023ea0d367297ffff010781 upstream.
Since commit c330fb1ddc0a ("XEN uses irqdesc::irq_data_common::handler_data to store a per interrupt XEN data pointer which contains XEN specific information.")
Xen is using the chip_data pointer for storing IRQ specific data. When
running as a HVM domain this can result in problems for legacy IRQs, as
those might use chip_data for their own purposes.
Use a local array for this purpose in case of legacy IRQs, avoiding the
double use.
Cc: stable@vger.kernel.org
Fixes: c330fb1ddc0a ("XEN uses irqdesc::irq_data_common::handler_data to store a per interrupt XEN data pointer which contains XEN specific information.")
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Stefan Bader <stefan.bader@canonical.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20200930091614.13660-1-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit c330fb1ddc0a922f044989492b7fcca77ee1db46 upstream.
handler data is meant for interrupt handlers and not for storing irq chip
specific information as some devices require handler data to store internal
per interrupt information, e.g. pinctrl/GPIO chained interrupt handlers.
This obviously creates a conflict of interests and crashes the machine
because the XEN pointer is overwritten by the driver pointer.
As the XEN data is not handler specific it should be stored in
irqdesc::irq_data::chip_data instead.
A simple sed s/irq_[sg]et_handler_data/irq_[sg]et_chip_data/ cures that.
Cc: stable@vger.kernel.org
Reported-by: Roman Shaposhnik <roman@zededa.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Roman Shaposhnik <roman@zededa.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/87lfi2yckt.fsf@nanos.tec.linutronix.de
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When binding an interdomain event channel to a vcpu via
IOCTL_EVTCHN_BIND_INTERDOMAIN not only the event channel needs to be
bound, but the affinity of the associated IRQi must be changed, too.
Otherwise the IRQ and the event channel won't be moved to another vcpu
in case the original vcpu they were bound to is going offline.
Cc: <stable@vger.kernel.org> # 4.13
Fixes: c48f64ab47 ("xen-evtchn: Bind dyn evtchn:qemu-dm interrupt to next online VCPU")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Add SPDX license identifiers to all files which:
- Have no license information of any form
- Have EXPORT_.*_SYMBOL_GPL inside which was used in the
initial scan/conversion to ignore the file
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
irq_ctx_init() is invoked from native_init_IRQ() or from xen_init_IRQ()
code. There is no reason to have this split. The interrupt stacks must be
allocated no matter what.
Invoke it from init_IRQ() before invoking the native or XEN init
implementation.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Josh Abraham <j.abraham1776@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: x86-ml <x86@kernel.org>
Cc: xen-devel@lists.xenproject.org
Link: https://lkml.kernel.org/r/20190414160146.001162606@linutronix.de
Commit f94c8d1169 ("sched/clock, x86/tsc: Rework the x86 'unstable'
sched_clock() interface") broke Xen guest time handling across
migration:
[ 187.249951] Freezing user space processes ... (elapsed 0.001 seconds) done.
[ 187.251137] OOM killer disabled.
[ 187.251137] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
[ 187.252299] suspending xenstore...
[ 187.266987] xen:grant_table: Grant tables using version 1 layout
[18446743811.706476] OOM killer enabled.
[18446743811.706478] Restarting tasks ... done.
[18446743811.720505] Setting capacity to 16777216
Fix that by setting xen_sched_clock_offset at resume time to ensure a
monotonic clock value.
[boris: replaced pr_info() with pr_info_once() in xen_callback_vector()
to avoid printing with incorrect timestamp during resume (as we
haven't re-adjusted the clock yet)]
Fixes: f94c8d1169 ("sched/clock, x86/tsc: Rework the x86 'unstable' sched_clock() interface")
Cc: <stable@vger.kernel.org> # 4.11
Reported-by: Hans van Kranenburg <hans.van.kranenburg@mendix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Tested-by: Hans van Kranenburg <hans.van.kranenburg@mendix.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Move remaining definitions and declarations from include/linux/bootmem.h
into include/linux/memblock.h and remove the redundant header.
The includes were replaced with the semantic patch below and then
semi-automated removal of duplicated '#include <linux/memblock.h>
@@
@@
- #include <linux/bootmem.h>
+ #include <linux/memblock.h>
[sfr@canb.auug.org.au: dma-direct: fix up for the removal of linux/bootmem.h]
Link: http://lkml.kernel.org/r/20181002185342.133d1680@canb.auug.org.au
[sfr@canb.auug.org.au: powerpc: fix up for removal of linux/bootmem.h]
Link: http://lkml.kernel.org/r/20181005161406.73ef8727@canb.auug.org.au
[sfr@canb.auug.org.au: x86/kaslr, ACPI/NUMA: fix for linux/bootmem.h removal]
Link: http://lkml.kernel.org/r/20181008190341.5e396491@canb.auug.org.au
Link: http://lkml.kernel.org/r/1536927045-23536-30-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Serge Semin <fancer.lancer@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch removes duplicate macro useage in events_base.c.
It also fixes gcc warning:
variable ‘col’ set but not used [-Wunused-but-set-variable]
Signed-off-by: Joshua Abraham <j.abraham1776@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Commit 910f8befdf ("xen/pirq: fix error path cleanup when binding
MSIs") fixed a couple of errors in error cleanup path of
xen_bind_pirq_msi_to_irq(). This cleanup allowed a call to
__unbind_from_irq() with an unbound irq, which would result in
triggering the BUG_ON there.
Since there is really no reason for the BUG_ON (xen_free_irq() can
operate on unbound irqs) we can remove it.
Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: stable@vger.kernel.org
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Current cleanup in the error path of xen_bind_pirq_msi_to_irq is
wrong. First of all there's an off-by-one in the cleanup loop, which
can lead to unbinding wrong IRQs.
Secondly IRQs not bound won't be freed, thus leaking IRQ numbers.
Note that there's no need to differentiate between bound and unbound
IRQs when freeing them, __unbind_from_irq will deal with both of them
correctly.
Fixes: 4892c9b4ad ("xen: add support for MSI message groups")
Reported-by: Hooman Mirhadi <mirhadih@amazon.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Amit Shah <aams@amazon.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
The only users of alloc_intr_gate() are hypervisors, which both check the
used_vectors bitmap whether they have allocated the gate already. Move that
check into alloc_intr_gate() and simplify the users.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064959.580830286@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Here is a device has xen-pirq-MSI interrupt. Dom0 might lost interrupt
during driver irq_disable/irq_enable. Here is the scenario,
1. irq_disable -> disable_dynirq -> mask_evtchn(irq channel)
2. dev interrupt raised by HW and Xen mark its evtchn as pending
3. irq_enable -> startup_pirq -> eoi_pirq ->
clear_evtchn(channel of irq) -> clear pending status
4. consume_one_event process the irq event without pending bit assert
which result in interrupt lost once
5. No HW interrupt raising anymore.
Now use enable_dynirq for enable_pirq of xen_pirq_chip to remove
eoi_pirq when irq_enable.
Signed-off-by: Liu Shuo <shuo.a.liu@intel.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Instead of fiddling with masking the event channels during suspend
and resume handling let do the irq subsystem do its job. It will do
the mask and unmask operations as needed.
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
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Merge tag 'for-linus-4.13-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull xen updates from Juergen Gross:
"Other than fixes and cleanups it contains:
- support > 32 VCPUs at domain restore
- support for new sysfs nodes related to Xen
- some performance tuning for Linux running as Xen guest"
* tag 'for-linus-4.13-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
x86/xen: allow userspace access during hypercalls
x86: xen: remove unnecessary variable in xen_foreach_remap_area()
xen: allocate page for shared info page from low memory
xen: avoid deadlock in xenbus driver
xen: add sysfs node for hypervisor build id
xen: sync include/xen/interface/version.h
xen: add sysfs node for guest type
doc,xen: document hypervisor sysfs nodes for xen
xen/vcpu: Handle xen_vcpu_setup() failure at boot
xen/vcpu: Handle xen_vcpu_setup() failure in hotplug
xen/pv: Fix OOPS on restore for a PV, !SMP domain
xen/pvh*: Support > 32 VCPUs at domain restore
xen/vcpu: Simplify xen_vcpu related code
xen-evtchn: Bind dyn evtchn:qemu-dm interrupt to next online VCPU
xen: avoid type warning in xchg_xen_ulong
xen: fix HYPERVISOR_dm_op() prototype
xen: don't print error message in case of missing Xenstore entry
arm/xen: Adjust one function call together with a variable assignment
arm/xen: Delete an error message for a failed memory allocation in __set_phys_to_machine_multi()
arm/xen: Improve a size determination in __set_phys_to_machine_multi()
Update the effective affinity mask when an interrupt was successfully
targeted to a CPU.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Link: http://lkml.kernel.org/r/20170619235446.799944725@linutronix.de
A HVM domian booting generates around 200K (evtchn:qemu-dm xen-dyn)
interrupts,in a short period of time. All these evtchn:qemu-dm are bound
to VCPU 0, until irqbalance sees these IRQ and moves it to a different VCPU.
In one configuration, irqbalance runs every 10 seconds, which means
irqbalance doesn't get to see these burst of interrupts and doesn't
re-balance interrupts most of the time, making all evtchn:qemu-dm to be
processed by VCPU0. This cause VCPU0 to spend most of time processing
hardirq and very little time on softirq. Moreover, if dom0 kernel PREEMPTION
is disabled, VCPU0 never runs watchdog (process context), triggering a
softlockup detection code to panic.
Binding evtchn:qemu-dm to next online VCPU, will spread hardirq
processing evenly across different CPU. Later, irqbalance will try to balance
evtchn:qemu-dm, if required.
Signed-off-by: Anoob Soman <anoob.soman@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Recent discussion (http://marc.info/?l=xen-devel&m=149192184523741)
established that commit 72a9b18629 ("xen: Remove event channel
notification through Xen PCI platform device") (and thus commit
da72ff5bfc ("partially revert "xen: Remove event channel
notification through Xen PCI platform device"")) are unnecessary and,
in fact, prevent HVM guests from booting on Xen releases prior to 4.0
Therefore we revert both of those commits.
The summary of that discussion is below:
Here is the brief summary of the current situation:
Before the offending commit (72a9b18629):
1) INTx does not work because of the reset_watches path.
2) The reset_watches path is only taken if you have Xen > 4.0
3) The Linux Kernel by default will use vector inject if the hypervisor
support. So even INTx does not work no body running the kernel with
Xen > 4.0 would notice. Unless he explicitly disabled this feature
either in the kernel or in Xen (and this can only be disabled by
modifying the code, not user-supported way to do it).
After the offending commit (+ partial revert):
1) INTx is no longer support for HVM (only for PV guests).
2) Any HVM guest The kernel will not boot on Xen < 4.0 which does
not have vector injection support. Since the only other mode
supported is INTx which.
So based on this summary, I think before commit (72a9b18629) we were
in much better position from a user point of view.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
We are replacing existing PVH guests with new implementation.
We are keeping xen_pvh_domain() macro (for now set to zero) because
when we introduce new PVH implementation later in this series we will
reuse current PVH-specific code (xen_pvh_gnttab_setup()), and that
code is conditioned by 'if (xen_pvh_domain())'. (We will also need
a noop xen_pvh_domain() for !CONFIG_XEN_PVH).
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Merge tag 'for-linus-4.10-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull xen updates from Juergen Gross:
"Xen features and fixes for 4.10
These are some fixes, a move of some arm related headers to share them
between arm and arm64 and a series introducing a helper to make code
more readable.
The most notable change is David stepping down as maintainer of the
Xen hypervisor interface. This results in me sending you the pull
requests for Xen related code from now on"
* tag 'for-linus-4.10-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: (29 commits)
xen/balloon: Only mark a page as managed when it is released
xenbus: fix deadlock on writes to /proc/xen/xenbus
xen/scsifront: don't request a slot on the ring until request is ready
xen/x86: Increase xen_e820_map to E820_X_MAX possible entries
x86: Make E820_X_MAX unconditionally larger than E820MAX
xen/pci: Bubble up error and fix description.
xen: xenbus: set error code on failure
xen: set error code on failures
arm/xen: Use alloc_percpu rather than __alloc_percpu
arm/arm64: xen: Move shared architecture headers to include/xen/arm
xen/events: use xen_vcpu_id mapping for EVTCHNOP_status
xen/gntdev: Use VM_MIXEDMAP instead of VM_IO to avoid NUMA balancing
xen-scsifront: Add a missing call to kfree
MAINTAINERS: update XEN HYPERVISOR INTERFACE
xenfs: Use proc_create_mount_point() to create /proc/xen
xen-platform: use builtin_pci_driver
xen-netback: fix error handling output
xen: make use of xenbus_read_unsigned() in xenbus
xen: make use of xenbus_read_unsigned() in xen-pciback
xen: make use of xenbus_read_unsigned() in xen-fbfront
...
One include less is always a good thing(tm). Good riddance.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20161209182912.2726-6-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
EVTCHNOP_status hypercall returns Xen's idea of vcpu id so we need to
compare it against xen_vcpu_id mapping, not the Linux cpu id.
Suggested-by: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Ever since commit 254d1a3f02 ("xen/pv-on-hvm kexec: shutdown watches
from old kernel") using the INTx interrupt from Xen PCI platform
device for event channel notification would just lockup the guest
during bootup. postcore_initcall now calls xs_reset_watches which
will eventually try to read a value from XenStore and will get stuck
on read_reply at XenBus forever since the platform driver is not
probed yet and its INTx interrupt handler is not registered yet. That
means that the guest can not be notified at this moment of any pending
event channels and none of the per-event handlers will ever be invoked
(including the XenStore one) and the reply will never be picked up by
the kernel.
The exact stack where things get stuck during xenbus_init:
-xenbus_init
-xs_init
-xs_reset_watches
-xenbus_scanf
-xenbus_read
-xs_single
-xs_single
-xs_talkv
Vector callbacks have always been the favourite event notification
mechanism since their introduction in commit 38e20b07ef ("x86/xen:
event channels delivery on HVM.") and the vector callback feature has
always been advertised for quite some time by Xen that's why INTx was
broken for several years now without impacting anyone.
Luckily this also means that event channel notification through INTx
is basically dead-code which can be safely removed without impacting
anybody since it has been effectively disabled for more than 4 years
with nobody complaining about it (at least as far as I'm aware of).
This commit removes event channel notification through Xen PCI
platform device.
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Julien Grall <julien.grall@citrix.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Ross Lagerwall <ross.lagerwall@citrix.com>
Cc: xen-devel@lists.xenproject.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Cc: Anthony Liguori <aliguori@amazon.com>
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
EVTCHNOP_bind_ipi and EVTCHNOP_bind_virq pass vCPU id as a parameter
and Xen's idea of vCPU id should be used. Use the newly introduced
xen_vcpu_id mapping to convert it from Linux's id.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
HYPERVISOR_vcpu_op() passes Linux's idea of vCPU id as a parameter
while Xen's idea is expected. In some cases these ideas diverge so we
need to do remapping.
Convert all callers of HYPERVISOR_vcpu_op() to use xen_vcpu_nr().
Leave xen_fill_possible_map() and xen_filter_cpu_maps() intact as
they're only being called by PV guests before perpu areas are
initialized. While the issue could be solved by switching to
early_percpu for xen_vcpu_id I think it's not worth it: PV guests will
probably never get to the point where their idea of vCPU id diverges
from Xen's.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Moving an unmasked irq may result in irq handler being invoked on both
source and target CPUs.
With 2-level this can happen as follows:
On source CPU:
evtchn_2l_handle_events() ->
generic_handle_irq() ->
handle_edge_irq() ->
eoi_pirq():
irq_move_irq(data);
/***** WE ARE HERE *****/
if (VALID_EVTCHN(evtchn))
clear_evtchn(evtchn);
If at this moment target processor is handling an unrelated event in
evtchn_2l_handle_events()'s loop it may pick up our event since target's
cpu_evtchn_mask claims that this event belongs to it *and* the event is
unmasked and still pending. At the same time, source CPU will continue
executing its own handle_edge_irq().
With FIFO interrupt the scenario is similar: irq_move_irq() may result
in a EVTCHNOP_unmask hypercall which, in turn, may make the event
pending on the target CPU.
We can avoid this situation by moving and clearing the event while
keeping event masked.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Code that uses no modular facilities whatsoever should not be
sourcing module.h at all, since that header drags in a bunch
of other headers with it.
Similarly, code that is not explicitly using modular facilities
like module_init() but only is declaring module_param setup
variables should be using moduleparam.h and not the larger
module.h file for that.
In making this change, we also uncover an implicit use of BUG()
in inline fcns within arch/arm/include/asm/xen/hypercall.h so
we explicitly source <linux/bug.h> for that file now.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
After commit 8c058b0b9c ("x86/irq: Probe for PIC presence before
allocating descs for legacy IRQs") early_irq_init() will no longer
preallocate descriptors for legacy interrupts if PIC does not
exist, which is the case for Xen PV guests.
Therefore we may need to allocate those descriptors ourselves.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Only use the first 4KB of the page to store the events channel info. It
means that we will waste 60KB every time we allocate page for:
* control block: a page is allocating per CPU
* event array: a page is allocating everytime we need to expand it
I think we can reduce the memory waste for the 2 areas by:
* control block: sharing between multiple vCPUs. Although it will
require some bookkeeping in order to not free the page when the CPU
goes offline and the other CPUs sharing the page still there
* event array: always extend the array event by 64K (i.e 16 4K
chunk). That would require more care when we fail to expand the
event channel.
Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
- Use the correct GFN/BFN terms more consistently.
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Merge tag 'for-linus-4.3-rc0b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull xen terminology fixes from David Vrabel:
"Use the correct GFN/BFN terms more consistently"
* tag 'for-linus-4.3-rc0b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
xen/xenbus: Rename the variable xen_store_mfn to xen_store_gfn
xen/privcmd: Further s/MFN/GFN/ clean-up
hvc/xen: Further s/MFN/GFN clean-up
video/xen-fbfront: Further s/MFN/GFN clean-up
xen/tmem: Use xen_page_to_gfn rather than pfn_to_gfn
xen: Use correctly the Xen memory terminologies
arm/xen: implement correctly pfn_to_mfn
xen: Make clear that swiotlb and biomerge are dealing with DMA address
- Convert xen-blkfront to the multiqueue API
- [arm] Support binding event channels to different VCPUs.
- [x86] Support > 512 GiB in a PV guests (off by default as such a
guest cannot be migrated with the current toolstack).
- [x86] PMU support for PV dom0 (limited support for using perf with
Xen and other guests).
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Merge tag 'for-linus-4.3-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip
Pull xen updates from David Vrabel:
"Xen features and fixes for 4.3:
- Convert xen-blkfront to the multiqueue API
- [arm] Support binding event channels to different VCPUs.
- [x86] Support > 512 GiB in a PV guests (off by default as such a
guest cannot be migrated with the current toolstack).
- [x86] PMU support for PV dom0 (limited support for using perf with
Xen and other guests)"
* tag 'for-linus-4.3-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: (33 commits)
xen: switch extra memory accounting to use pfns
xen: limit memory to architectural maximum
xen: avoid another early crash of memory limited dom0
xen: avoid early crash of memory limited dom0
arm/xen: Remove helpers which are PV specific
xen/x86: Don't try to set PCE bit in CR4
xen/PMU: PMU emulation code
xen/PMU: Intercept PMU-related MSR and APIC accesses
xen/PMU: Describe vendor-specific PMU registers
xen/PMU: Initialization code for Xen PMU
xen/PMU: Sysfs interface for setting Xen PMU mode
xen: xensyms support
xen: remove no longer needed p2m.h
xen: allow more than 512 GB of RAM for 64 bit pv-domains
xen: move p2m list if conflicting with e820 map
xen: add explicit memblock_reserve() calls for special pages
mm: provide early_memremap_ro to establish read-only mapping
xen: check for initrd conflicting with e820 map
xen: check pre-allocated page tables for conflict with memory map
xen: check for kernel memory conflicting with memory layout
...
Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN
is meant, I suspect this is because the first support for Xen was for
PV. This resulted in some misimplementation of helpers on ARM and
confused developers about the expected behavior.
For instance, with pfn_to_mfn, we expect to get an MFN based on the name.
Although, if we look at the implementation on x86, it's returning a GFN.
For clarity and avoid new confusion, replace any reference to mfn with
gfn in any helpers used by PV drivers. The x86 code will still keep some
reference of pfn_to_mfn which may be used by all kind of guests
No changes as been made in the hypercall field, even
though they may be invalid, in order to keep the same as the defintion
in xen repo.
Note that page_to_mfn has been renamed to xen_page_to_gfn to avoid a
name to close to the KVM function gfn_to_page.
Take also the opportunity to simplify simple construction such
as pfn_to_mfn(page_to_pfn(page)) into xen_page_to_gfn. More complex clean up
will come in follow-up patches.
[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=e758ed14f390342513405dd766e874934573e6cb
Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Currently, the event channel rebind code is gated with the presence of
the vector callback.
The virtual interrupt controller on ARM has the concept of per-CPU
interrupt (PPI) which allow us to support per-VCPU event channel.
Therefore there is no need of vector callback for ARM.
Xen is already using a free PPI to notify the guest VCPU of an event.
Furthermore, the xen code initialization in Linux (see
arch/arm/xen/enlighten.c) is requesting correctly a per-CPU IRQ.
Introduce new helper xen_support_evtchn_rebind to allow architecture
decide whether rebind an event is support or not. It will always return
true on ARM and keep the same behavior on x86.
This is also allow us to drop the usage of xen_have_vector_callback
entirely in the ARM code.
Signed-off-by: Julien Grall <julien.grall@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This reverts commit fcdf31a7c1.
This was causing a WARNING whenever a PIRQ was closed since
shutdown_pirq() is called with irqs disabled.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Cc: <stable@vger.kernel.org>
An event channel bound to a CPU that was offlined may still be linked
on that CPU's queue. If this event channel is closed and reused,
subsequent events will be lost because the event channel is never
unlinked and thus cannot be linked onto the correct queue.
When a channel is closed and the event is still linked into a queue,
ensure that it is unlinked before completing.
If the CPU to which the event channel bound is online, spin until the
event is handled by that CPU. If that CPU is offline, it can't handle
the event, so clear the event queue during the close, dropping the
events.
This fixes the missing interrupts (and subsequent disk stalls etc.)
when offlining a CPU.
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Maximilian Heyne