Re: [PATCH v3 6/8] KVM-HV: Add flush_on_enter before guest enter

[Marcelo Tosatti <mtosatti@redhat.com>]

On Tue, Jul 31, 2012 at 04:19:02PM +0530, Nikunj A. Dadhania wrote:
> From: Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com>
> 
> PV-Flush guest would indicate to flush on enter, flush the TLB before
> entering and exiting the guest.
> 
> Signed-off-by: Nikunj A. Dadhania <nikunj@linux.vnet.ibm.com>
> ---
>  arch/x86/kvm/x86.c |   23 +++++++----------------
>  1 files changed, 7 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 580abcf..a67e971 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1557,20 +1557,9 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
>  		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
>  }
>  
> -static void kvm_set_atomic(u64 *addr, u64 old, u64 new)
> -{
> -	int loop = 1000000;
> -	while (1) {
> -		if (cmpxchg(addr, old, new) == old)
> -			break;
> -		loop--;
> -		if (!loop) {
> -			pr_info("atomic cur: %lx old: %lx new: %lx\n",
> -				*addr, old, new);
> -			break;
> -		}
> -	}
> -}
> +#define VS_NOT_IN_GUEST      (0)
> +#define VS_IN_GUEST          (1 << KVM_VCPU_STATE_IN_GUEST_MODE)
> +#define VS_SHOULD_FLUSH      (1 << KVM_VCPU_STATE_SHOULD_FLUSH)
>  
>  static void kvm_set_vcpu_state(struct kvm_vcpu *vcpu)
>  {
> @@ -1584,7 +1573,8 @@ static void kvm_set_vcpu_state(struct kvm_vcpu *vcpu)
>  	kaddr = kmap_atomic(vcpu->arch.v_state.vs_page);
>  	kaddr += vcpu->arch.v_state.vs_offset;
>  	vs = kaddr;
> -	kvm_set_atomic(&vs->state, 0, 1 << KVM_VCPU_STATE_IN_GUEST_MODE);
> +	if (xchg(&vs->state, VS_IN_GUEST) == VS_SHOULD_FLUSH)
> +		kvm_x86_ops->tlb_flush(vcpu);
>  	kunmap_atomic(kaddr);
>  }
>  
> @@ -1600,7 +1590,8 @@ static void kvm_clear_vcpu_state(struct kvm_vcpu *vcpu)
>  	kaddr = kmap_atomic(vcpu->arch.v_state.vs_page);
>  	kaddr += vcpu->arch.v_state.vs_offset;
>  	vs = kaddr;
> -	kvm_set_atomic(&vs->state, 1 << KVM_VCPU_STATE_IN_GUEST_MODE, 0);
> +	if (xchg(&vs->state, VS_NOT_IN_GUEST) == VS_SHOULD_FLUSH)
> +		kvm_x86_ops->tlb_flush(vcpu);
>  	kunmap_atomic(kaddr);
>  }

Nevermind the early comment (the other comments on that message are
valid).