| Message ID | 1509241736-99913-1-git-send-email-christoffer.dall@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Oct 29 2017 at 2:48:56 am GMT, Christoffer Dall <christoffer.dall@linaro.org> wrote: > After being lazy with saving/restoring the timer state, we defer that > work to vcpu_load and vcpu_put, which ensure that the timer state is > loaded on the hardware timers whenever the VCPU runs. > > Unfortunately, we are failing to do that the first time vcpu_load() > runs, because the timer has not yet been enabled at that time. As long > as the initialized timer state matches what happens to be in the > hardware (a disabled timer, because we never leave the timer screaming), > this does not show up as a problem, but is nevertheless incorrect. > > The solution is simple; disable preemption while setting the timer to be > enabled, and call the timer load function when first enabling the timer. > > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com> M.
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index 2035cf2..4db54ff 100644 --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -861,7 +861,11 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu) return ret; no_vgic: + preempt_disable(); timer->enabled = 1; + kvm_timer_vcpu_load_vgic(vcpu); + preempt_enable(); + return 0; }
After being lazy with saving/restoring the timer state, we defer that work to vcpu_load and vcpu_put, which ensure that the timer state is loaded on the hardware timers whenever the VCPU runs. Unfortunately, we are failing to do that the first time vcpu_load() runs, because the timer has not yet been enabled at that time. As long as the initialized timer state matches what happens to be in the hardware (a disabled timer, because we never leave the timer screaming), this does not show up as a problem, but is nevertheless incorrect. The solution is simple; disable preemption while setting the timer to be enabled, and call the timer load function when first enabling the timer. Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> --- virt/kvm/arm/arch_timer.c | 4 ++++ 1 file changed, 4 insertions(+)