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d35268da66
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>
77 lines
2.2 KiB
C
77 lines
2.2 KiB
C
/*
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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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struct arch_timer_kvm {
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/* Is the timer enabled */
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bool enabled;
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/* Virtual offset */
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cycle_t cntvoff;
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};
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struct arch_timer_cpu {
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/* Registers: control register, timer value */
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u32 cntv_ctl; /* Saved/restored */
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cycle_t cntv_cval; /* Saved/restored */
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/*
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* Anything that is not used directly from assembly code goes
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* here.
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*/
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/* Background timer used when the guest is not running */
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struct hrtimer timer;
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/* Work queued with the above timer expires */
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struct work_struct expired;
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/* Background timer active */
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bool armed;
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/* Timer IRQ */
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const struct kvm_irq_level *irq;
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/* VGIC mapping */
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struct irq_phys_map *map;
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};
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int kvm_timer_hyp_init(void);
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void kvm_timer_enable(struct kvm *kvm);
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void kvm_timer_init(struct kvm *kvm);
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int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
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const struct kvm_irq_level *irq);
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void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu);
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void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu);
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void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu);
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void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu);
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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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bool kvm_timer_should_fire(struct kvm_vcpu *vcpu);
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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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#endif
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