2013-01-24 02:21:58 +08:00
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/*
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* Copyright (C) 2012 ARM Ltd.
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* Author: Marc Zyngier <marc.zyngier@arm.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef __ASM_ARM_KVM_ARCH_TIMER_H
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#define __ASM_ARM_KVM_ARCH_TIMER_H
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#include <linux/clocksource.h>
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#include <linux/hrtimer.h>
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#include <linux/workqueue.h>
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2017-02-03 23:19:59 +08:00
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struct arch_timer_context {
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2013-01-24 02:21:58 +08:00
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/* Registers: control register, timer value */
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2017-02-03 23:19:59 +08:00
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u32 cnt_ctl;
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u64 cnt_cval;
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/* Timer IRQ */
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struct kvm_irq_level irq;
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KVM: arm/arm64: Avoid timer save/restore in vcpu entry/exit
We don't need to save and restore the hardware timer state and examine
if it generates interrupts on on every entry/exit to the guest. The
timer hardware is perfectly capable of telling us when it has expired
by signaling interrupts.
When taking a vtimer interrupt in the host, we don't want to mess with
the timer configuration, we just want to forward the physical interrupt
to the guest as a virtual interrupt. We can use the split priority drop
and deactivate feature of the GIC to do this, which leaves an EOI'ed
interrupt active on the physical distributor, making sure we don't keep
taking timer interrupts which would prevent the guest from running. We
can then forward the physical interrupt to the VM using the HW bit in
the LR of the GIC, like we do already, which lets the guest directly
deactivate both the physical and virtual timer simultaneously, allowing
the timer hardware to exit the VM and generate a new physical interrupt
when the timer output is again asserted later on.
We do need to capture this state when migrating VCPUs between physical
CPUs, however, which we use the vcpu put/load functions for, which are
called through preempt notifiers whenever the thread is scheduled away
from the CPU or called directly if we return from the ioctl to
userspace.
One caveat is that we have to save and restore the timer state in both
kvm_timer_vcpu_[put/load] and kvm_timer_[schedule/unschedule], because
we can have the following flows:
1. kvm_vcpu_block
2. kvm_timer_schedule
3. schedule
4. kvm_timer_vcpu_put (preempt notifier)
5. schedule (vcpu thread gets scheduled back)
6. kvm_timer_vcpu_load (preempt notifier)
7. kvm_timer_unschedule
And a version where we don't actually call schedule:
1. kvm_vcpu_block
2. kvm_timer_schedule
7. kvm_timer_unschedule
Since kvm_timer_[schedule/unschedule] may not be followed by put/load,
but put/load also may be called independently, we call the timer
save/restore functions from both paths. Since they rely on the loaded
flag to never save/restore when unnecessary, this doesn't cause any
harm, and we ensure that all invokations of either set of functions work
as intended.
An added benefit beyond not having to read and write the timer sysregs
on every entry and exit is that we no longer have to actively write the
active state to the physical distributor, because we configured the
irq for the vtimer to only get a priority drop when handling the
interrupt in the GIC driver (we called irq_set_vcpu_affinity()), and
the interrupt stays active after firing on the host.
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
2016-10-17 02:30:38 +08:00
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/*
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* We have multiple paths which can save/restore the timer state
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* onto the hardware, so we need some way of keeping track of
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* where the latest state is.
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*
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* loaded == true: State is loaded on the hardware registers.
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* loaded == false: State is stored in memory.
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*/
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bool loaded;
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2017-02-03 23:20:00 +08:00
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/* Virtual offset */
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u64 cntvoff;
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2017-02-03 23:19:59 +08:00
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};
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2013-01-24 02:21:58 +08:00
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2017-02-03 23:19:59 +08:00
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struct arch_timer_cpu {
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struct arch_timer_context vtimer;
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2017-02-03 23:20:02 +08:00
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struct arch_timer_context ptimer;
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2013-01-24 02:21:58 +08:00
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/* Background timer used when the guest is not running */
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2017-06-17 22:33:02 +08:00
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struct hrtimer bg_timer;
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2013-01-24 02:21:58 +08:00
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/* Work queued with the above timer expires */
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struct work_struct expired;
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2017-06-18 15:32:08 +08:00
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/* Physical timer emulation */
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struct hrtimer phys_timer;
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2016-05-18 23:26:00 +08:00
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/* Is the timer enabled */
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bool enabled;
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2013-01-24 02:21:58 +08:00
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};
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2017-12-07 19:46:15 +08:00
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int kvm_timer_hyp_init(bool);
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2016-05-18 23:26:00 +08:00
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int kvm_timer_enable(struct kvm_vcpu *vcpu);
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2017-05-03 02:14:06 +08:00
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int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu);
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2013-01-24 02:21:58 +08:00
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void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu);
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void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu);
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KVM: arm/arm64: Support arch timers with a userspace gic
If you're running with a userspace gic or other interrupt controller
(that is no vgic in the kernel), then you have so far not been able to
use the architected timers, because the output of the architected
timers, which are driven inside the kernel, was a kernel-only construct
between the arch timer code and the vgic.
This patch implements the new KVM_CAP_ARM_USER_IRQ feature, where we use a
side channel on the kvm_run structure, run->s.regs.device_irq_level, to
always notify userspace of the timer output levels when using a userspace
irqchip.
This works by ensuring that before we enter the guest, if the timer
output level has changed compared to what we last told userspace, we
don't enter the guest, but instead return to userspace to notify it of
the new level. If we are exiting, because of an MMIO for example, and
the level changed at the same time, the value is also updated and
userspace can sample the line as it needs. This is nicely achieved
simply always updating the timer_irq_level field after the main run
loop.
Note that the kvm_timer_update_irq trace event is changed to show the
host IRQ number for the timer instead of the guest IRQ number, because
the kernel no longer know which IRQ userspace wires up the timer signal
to.
Also note that this patch implements all required functionality but does
not yet advertise the capability.
Reviewed-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
2016-09-28 03:08:06 +08:00
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bool kvm_timer_should_notify_user(struct kvm_vcpu *vcpu);
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void kvm_timer_update_run(struct kvm_vcpu *vcpu);
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2013-01-24 02:21:58 +08:00
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void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu);
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2014-07-04 22:54:14 +08:00
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u64 kvm_arm_timer_get_reg(struct kvm_vcpu *, u64 regid);
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int kvm_arm_timer_set_reg(struct kvm_vcpu *, u64 regid, u64 value);
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2017-05-03 02:19:15 +08:00
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int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
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int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
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int kvm_arm_timer_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
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2017-01-06 23:07:48 +08:00
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bool kvm_timer_is_pending(struct kvm_vcpu *vcpu);
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arm/arm64: KVM: arch_timer: Only schedule soft timer on vcpu_block
We currently schedule a soft timer every time we exit the guest if the
timer did not expire while running the guest. This is really not
necessary, because the only work we do in the timer work function is to
kick the vcpu.
Kicking the vcpu does two things:
(1) If the vpcu thread is on a waitqueue, make it runnable and remove it
from the waitqueue.
(2) If the vcpu is running on a different physical CPU from the one
doing the kick, it sends a reschedule IPI.
The second case cannot happen, because the soft timer is only ever
scheduled when the vcpu is not running. The first case is only relevant
when the vcpu thread is on a waitqueue, which is only the case when the
vcpu thread has called kvm_vcpu_block().
Therefore, we only need to make sure a timer is scheduled for
kvm_vcpu_block(), which we do by encapsulating all calls to
kvm_vcpu_block() with kvm_timer_{un}schedule calls.
Additionally, we only schedule a soft timer if the timer is enabled and
unmasked, since it is useless otherwise.
Note that theoretically userspace can use the SET_ONE_REG interface to
change registers that should cause the timer to fire, even if the vcpu
is blocked without a scheduled timer, but this case was not supported
before this patch and we leave it for future work for now.
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
2015-08-26 01:48:21 +08:00
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void kvm_timer_schedule(struct kvm_vcpu *vcpu);
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void kvm_timer_unschedule(struct kvm_vcpu *vcpu);
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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 01:02:55 +08:00
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2017-02-03 23:20:08 +08:00
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u64 kvm_phys_timer_read(void);
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KVM: arm/arm64: Avoid timer save/restore in vcpu entry/exit
We don't need to save and restore the hardware timer state and examine
if it generates interrupts on on every entry/exit to the guest. The
timer hardware is perfectly capable of telling us when it has expired
by signaling interrupts.
When taking a vtimer interrupt in the host, we don't want to mess with
the timer configuration, we just want to forward the physical interrupt
to the guest as a virtual interrupt. We can use the split priority drop
and deactivate feature of the GIC to do this, which leaves an EOI'ed
interrupt active on the physical distributor, making sure we don't keep
taking timer interrupts which would prevent the guest from running. We
can then forward the physical interrupt to the VM using the HW bit in
the LR of the GIC, like we do already, which lets the guest directly
deactivate both the physical and virtual timer simultaneously, allowing
the timer hardware to exit the VM and generate a new physical interrupt
when the timer output is again asserted later on.
We do need to capture this state when migrating VCPUs between physical
CPUs, however, which we use the vcpu put/load functions for, which are
called through preempt notifiers whenever the thread is scheduled away
from the CPU or called directly if we return from the ioctl to
userspace.
One caveat is that we have to save and restore the timer state in both
kvm_timer_vcpu_[put/load] and kvm_timer_[schedule/unschedule], because
we can have the following flows:
1. kvm_vcpu_block
2. kvm_timer_schedule
3. schedule
4. kvm_timer_vcpu_put (preempt notifier)
5. schedule (vcpu thread gets scheduled back)
6. kvm_timer_vcpu_load (preempt notifier)
7. kvm_timer_unschedule
And a version where we don't actually call schedule:
1. kvm_vcpu_block
2. kvm_timer_schedule
7. kvm_timer_unschedule
Since kvm_timer_[schedule/unschedule] may not be followed by put/load,
but put/load also may be called independently, we call the timer
save/restore functions from both paths. Since they rely on the loaded
flag to never save/restore when unnecessary, this doesn't cause any
harm, and we ensure that all invokations of either set of functions work
as intended.
An added benefit beyond not having to read and write the timer sysregs
on every entry and exit is that we no longer have to actively write the
active state to the physical distributor, because we configured the
irq for the vtimer to only get a priority drop when handling the
interrupt in the GIC driver (we called irq_set_vcpu_affinity()), and
the interrupt stays active after firing on the host.
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
2016-10-17 02:30:38 +08:00
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void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu);
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2016-01-30 03:04:48 +08:00
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void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu);
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2016-12-02 03:32:05 +08:00
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void kvm_timer_init_vhe(void);
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2017-02-03 23:19:59 +08:00
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#define vcpu_vtimer(v) (&(v)->arch.timer_cpu.vtimer)
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2017-02-03 23:20:02 +08:00
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#define vcpu_ptimer(v) (&(v)->arch.timer_cpu.ptimer)
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KVM: arm/arm64: Avoid timer save/restore in vcpu entry/exit
We don't need to save and restore the hardware timer state and examine
if it generates interrupts on on every entry/exit to the guest. The
timer hardware is perfectly capable of telling us when it has expired
by signaling interrupts.
When taking a vtimer interrupt in the host, we don't want to mess with
the timer configuration, we just want to forward the physical interrupt
to the guest as a virtual interrupt. We can use the split priority drop
and deactivate feature of the GIC to do this, which leaves an EOI'ed
interrupt active on the physical distributor, making sure we don't keep
taking timer interrupts which would prevent the guest from running. We
can then forward the physical interrupt to the VM using the HW bit in
the LR of the GIC, like we do already, which lets the guest directly
deactivate both the physical and virtual timer simultaneously, allowing
the timer hardware to exit the VM and generate a new physical interrupt
when the timer output is again asserted later on.
We do need to capture this state when migrating VCPUs between physical
CPUs, however, which we use the vcpu put/load functions for, which are
called through preempt notifiers whenever the thread is scheduled away
from the CPU or called directly if we return from the ioctl to
userspace.
One caveat is that we have to save and restore the timer state in both
kvm_timer_vcpu_[put/load] and kvm_timer_[schedule/unschedule], because
we can have the following flows:
1. kvm_vcpu_block
2. kvm_timer_schedule
3. schedule
4. kvm_timer_vcpu_put (preempt notifier)
5. schedule (vcpu thread gets scheduled back)
6. kvm_timer_vcpu_load (preempt notifier)
7. kvm_timer_unschedule
And a version where we don't actually call schedule:
1. kvm_vcpu_block
2. kvm_timer_schedule
7. kvm_timer_unschedule
Since kvm_timer_[schedule/unschedule] may not be followed by put/load,
but put/load also may be called independently, we call the timer
save/restore functions from both paths. Since they rely on the loaded
flag to never save/restore when unnecessary, this doesn't cause any
harm, and we ensure that all invokations of either set of functions work
as intended.
An added benefit beyond not having to read and write the timer sysregs
on every entry and exit is that we no longer have to actively write the
active state to the physical distributor, because we configured the
irq for the vtimer to only get a priority drop when handling the
interrupt in the GIC driver (we called irq_set_vcpu_affinity()), and
the interrupt stays active after firing on the host.
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
2016-10-17 02:30:38 +08:00
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2013-01-24 02:21:58 +08:00
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#endif
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