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KVM: arm/arm64: Set up a background timer for the physical timer emulation

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Set a background timer for the EL1 physical timer emulation while VMs
are running, so that VMs get the physical timer interrupts in a timely
manner.

Schedule the background timer on entry to the VM and cancel it on exit.
This would not have any performance impact to the guest OSes that
currently use the virtual timer since the physical timer is always not
enabled.

Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Jintack Lim 2017-02-03 10:20:06 -05:00 committed by Marc Zyngier
parent fb280e9757
commit f242adaf0c
1 changed files with 24 additions and 1 deletions
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25
virt/kvm/arm/arch_timer.c
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@ -229,6 +229,22 @@ static int kvm_timer_update_state(struct kvm_vcpu *vcpu)
return 0; return 0;
} }
/* Schedule the background timer for the emulated timer. */
static void kvm_timer_emulate(struct kvm_vcpu *vcpu,
struct arch_timer_context *timer_ctx)
{
struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
if (kvm_timer_should_fire(timer_ctx))
return;
if (!kvm_timer_irq_can_fire(timer_ctx))
return;
/* The timer has not yet expired, schedule a background timer */
timer_arm(timer, kvm_timer_compute_delta(timer_ctx));
}
/* /*
* Schedule the background timer before calling kvm_vcpu_block, so that this * Schedule the background timer before calling kvm_vcpu_block, so that this
* thread is removed from its waitqueue and made runnable when there's a timer * thread is removed from its waitqueue and made runnable when there's a timer
@ -286,6 +302,9 @@ void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu)
if (kvm_timer_update_state(vcpu)) if (kvm_timer_update_state(vcpu))
return; return;
/* Set the background timer for the physical timer emulation. */
kvm_timer_emulate(vcpu, vcpu_ptimer(vcpu));
/* /*
* If we enter the guest with the virtual input level to the VGIC * If we enter the guest with the virtual input level to the VGIC
* asserted, then we have already told the VGIC what we need to, and * asserted, then we have already told the VGIC what we need to, and
@ -348,7 +367,11 @@ void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
{ {
struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
BUG_ON(timer_is_armed(timer)); /*
* This is to cancel the background timer for the physical timer
* emulation if it is set.
*/
timer_disarm(timer);
/* /*
* The guest could have modified the timer registers or the timer * The guest could have modified the timer registers or the timer