Re: [PATCH] KVM: booke: Do Not start decrementer when SPRN_DEC set 0

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On 20.10.2011, at 10:15, Bhushan Bharat-R65777 wrote:

> 
> 
>> -----Original Message-----
>> From: kvm-ppc-owner@xxxxxxxxxxxxxxx [mailto:kvm-ppc-
>> owner@xxxxxxxxxxxxxxx] On Behalf Of Alexander Graf
>> Sent: Thursday, October 20, 2011 10:40 PM
>> To: Bhushan Bharat-R65777
>> Cc: kvm-ppc@xxxxxxxxxxxxxxx; bharatb.yadav@xxxxxxxxx; Bhushan Bharat-
>> R65777
>> Subject: Re: [PATCH] KVM: booke: Do Not start decrementer when SPRN_DEC
>> set 0
>> 
>> 
>> On 17.10.2011, at 20:37, Bharat Bhushan wrote:
>> 
>>> As per specification the decrementer interrupt not happen when DEC is
>> written with 0. So we should not start hrtimer with timeout = 0 as well.
>>> 
>>> Signed-off-by: Bharat Bhushan <bharat.bhushan@xxxxxxxxxxxxx>
>>> ---
>>> arch/powerpc/kvm/emulate.c |    8 ++++----
>>> 1 files changed, 4 insertions(+), 4 deletions(-)
>>> 
>>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>>> index 141dce3..8af3bad 100644
>>> --- a/arch/powerpc/kvm/emulate.c
>>> +++ b/arch/powerpc/kvm/emulate.c
>>> @@ -70,14 +70,14 @@
>>> #define OP_STHU 45
>>> 
>>> #ifdef CONFIG_PPC_BOOK3S
>>> -static int kvmppc_dec_enabled(struct kvm_vcpu *vcpu)
>>> +static bool kvmppc_dec_enabled(struct kvm_vcpu *vcpu)
>>> {
>>> -	return 1;
>>> +	return true;
>> 
>> It's not necessary to change it to bool. The function will be inlined
>> anyways.
> 
> Ok, 
> I just thought that having bool will give more clarity.

If you really feel like it should be bool, we can change it in another patch. It certainly doesn't belong in this one :).

> 
>> 
>>> }
>>> #else
>>> -static int kvmppc_dec_enabled(struct kvm_vcpu *vcpu)
>>> +static bool kvmppc_dec_enabled(struct kvm_vcpu *vcpu)
>>> {
>>> -	return vcpu->arch.tcr & TCR_DIE;
>>> +	return (vcpu->arch.tcr & TCR_DIE) && !vcpu->arch.dec;
>> 
>> This means we declare the dec as enabled only when dec==0, no?
> 
> Will change this, 
> Functionally with dec = 0, it is as good as not enabled.

Yup :)


Alex

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