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KVM: arm/arm64: Fix timer enable flow

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When enabling the timer on the first run, we fail to ever restore the
state and mark it as loaded.  That means, that in the initial entry to
the VCPU ioctl, unless we exit to userspace for some reason such as a
pending signal, if the guest programs a timer and blocks, we will wait
forever, because we never read back the hardware state (the loaded flag
is not set), and so we think the timer is disabled, and we never
schedule a background soft timer.

The end result?  The VCPU blocks forever, and the only solution is to
kill the thread.

Fixes: 4a2c4da125 ("arm/arm64: KVM: Load the timer state when enabling the timer")
Reported-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
This commit is contained in:
Christoffer Dall 2017-12-15 00:30:12 +01:00
parent 36e5cfd410
commit 0eb7c33cad
1 changed files with 1 additions and 4 deletions
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5
virt/kvm/arm/arch_timer.c
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@ -846,10 +846,7 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu)
no_vgic:
preempt_disable();
timer->enabled = 1;
if (!irqchip_in_kernel(vcpu->kvm))
kvm_timer_vcpu_load_user(vcpu);
else
kvm_timer_vcpu_load_vgic(vcpu);
kvm_timer_vcpu_load(vcpu);
preempt_enable();
return 0;