linux/arch
Christoffer Dall 1a74847885 arm/arm64: KVM: Fix migration race in the arch timer
When a VCPU is no longer running, we currently check to see if it has a
timer scheduled in the future, and if it does, we schedule a host
hrtimer to notify is in case the timer expires while the VCPU is still
not running.  When the hrtimer fires, we mask the guest's timer and
inject the timer IRQ (still relying on the guest unmasking the time when
it receives the IRQ).

This is all good and fine, but when migration a VM (checkpoint/restore)
this introduces a race.  It is unlikely, but possible, for the following
sequence of events to happen:

 1. Userspace stops the VM
 2. Hrtimer for VCPU is scheduled
 3. Userspace checkpoints the VGIC state (no pending timer interrupts)
 4. The hrtimer fires, schedules work in a workqueue
 5. Workqueue function runs, masks the timer and injects timer interrupt
 6. Userspace checkpoints the timer state (timer masked)

At restore time, you end up with a masked timer without any timer
interrupts and your guest halts never receiving timer interrupts.

Fix this by only kicking the VCPU in the workqueue function, and sample
the expired state of the timer when entering the guest again and inject
the interrupt and mask the timer only then.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
2015-03-14 13:48:00 +01:00
..
alpha asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
arc Merge branch 'for-linus' of git://git.infradead.org/users/vkoul/slave-dma 2015-02-18 08:49:20 -08:00
arm arm/arm64: KVM: Fix migration race in the arch timer 2015-03-14 13:48:00 +01:00
arm64 arm/arm64: KVM: Implement Stage-2 page aging 2015-03-12 22:34:43 +01:00
avr32 asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
blackfin Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2015-02-21 12:59:04 -08:00
c6x all arches, signal: move restart_block to struct task_struct 2015-02-12 18:54:12 -08:00
cris CRIS changes for 3.20 2015-02-15 18:02:02 -08:00
frv asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
hexagon all arches, signal: move restart_block to struct task_struct 2015-02-12 18:54:12 -08:00
ia64 asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
m32r asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
m68k asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
metag asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
microblaze all arches, signal: move restart_block to struct task_struct 2015-02-12 18:54:12 -08:00
mips Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2015-02-21 19:41:38 -08:00
mn10300 OK, this has the big virtio 1.0 implementation, as specified by OASIS. 2015-02-18 09:24:01 -08:00
nios2 nios2 for v3.20 2015-02-17 14:23:42 -08:00
openrisc asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
parisc Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2015-02-19 10:07:08 -08:00
powerpc The clock framework changes for 3.20 contain the usual driver additions, 2015-02-21 12:30:30 -08:00
s390 Merge branch 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-02-22 17:42:14 -08:00
score all arches, signal: move restart_block to struct task_struct 2015-02-12 18:54:12 -08:00
sh asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
sparc asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
tile tile: use %*pb[l] to print bitmaps including cpumasks and nodemasks 2015-02-13 21:21:37 -08:00
um all arches, signal: move restart_block to struct task_struct 2015-02-12 18:54:12 -08:00
unicore32 mm: vmalloc: pass additional vm_flags to __vmalloc_node_range() 2015-02-13 21:21:42 -08:00
x86 KVM: emulate: fix CMPXCHG8B on 32-bit hosts 2015-02-23 22:28:48 +01:00
xtensa asm-generic: uaccess.h cleanup 2015-02-18 10:02:24 -08:00
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