Subject: [PATCH v5 2/4] ARM: KVM: arch_timers: Add guest timer core support

From: [email-masked] (Marc Zyngier)
Date: Tue, 15 Jan 2013 11:07:20 +0000

On 14/01/13 19:19, Christoffer Dall wrote:
> On Mon, Jan 14, 2013 at 10:18 AM, Will Deacon <[email-masked]> wrote:
>> On Tue, Jan 08, 2013 at 06:43:20PM +0000, Christoffer Dall wrote:
>>> From: Marc Zyngier <[email-masked]>
>>>
>>> Add some the architected timer related infrastructure, and support timer
>>> interrupt injection, which can happen as a resultof three possible
>>> events:
>>>
>>> - The virtual timer interrupt has fired while we were still
>>>   executing the guest
>>> - The timer interrupt hasn't fired, but it expired while we
>>>   were doing the world switch
>>> - A hrtimer we programmed earlier has fired
>>
>> [...]
>>
>>> +void kvm_timer_sync_to_cpu(struct kvm_vcpu *vcpu)
>>> +{
>>> +       struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
>>> +
>>> +       /*
>>> +        * We're about to run this vcpu again, so there is no need to
>>> +        * keep the background timer running, as we're about to
>>> +        * populate the CPU timer again.
>>> +        */
>>> +       timer_disarm(timer);
>>> +}
>>> +
>>> +void kvm_timer_sync_from_cpu(struct kvm_vcpu *vcpu)
>>> +{
>>> +       struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
>>> +       cycle_t cval, now;
>>> +       u64 ns;
>>> +
>>> +       /* Check if the timer is enabled and unmasked first */
>>> +       if ((timer->cntv_ctl & 3) != 1)
>>> +               return;
>>> +
>>> +       cval = timer->cntv_cval;
>>> +       now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
>>> +
>>> +       BUG_ON(timer_is_armed(timer));
>>> +
>>> +       if (cval <= now) {
>>> +               /*
>>> +                * Timer has already expired while we were not
>>> +                * looking. Inject the interrupt and carry on.
>>> +                */
>>> +               kvm_timer_inject_irq(vcpu);
>>> +               return;
>>> +       }
>>> +
>>> +       ns = cyclecounter_cyc2ns(timecounter->cc, cval - now);
>>> +       timer_arm(timer, ns);
>>> +}
>>
>> Please use flush/sync terminology to match the rest of arch/arm/.
>>
> ok, the following fixes this for both timers and the vgic:
> 
> commit 1b68f39459dbc797f6766c103edf2c1053984161
> Author: Christoffer Dall <[email-masked]>
> Date:   Mon Jan 14 14:16:31 2013 -0500
> 
>     KVM: ARM: vgic: use sync/flush terminology
> 
>     Use sync/flush for saving state to/from CPUs to be consistent with
>     other uses in arch/arm.

Sync and flush on their own are pretty inexpressive. Consider changing
it to {flush,sync}_hwstate, so we're consistent with what VFP does.

	M.
-- 
Jazz is not dead. It just smells funny...