Re: [PATCH 6/8] KVM: PPC: E500: Implement MMU notifiers

[Avi Kivity <avi@redhat.com>]

On 08/07/2012 01:57 PM, Alexander Graf wrote:
> The e500 target has lived without mmu notifiers ever since it got
> introduced, but fails for the user space check on them with hugetlbfs.
> 
> So in order to get that one working, implement mmu notifiers in a
> reasonably dumb fashion and be happy. On embedded hardware, we almost
> never end up with mmu notifier calls, since most people don't overcommit.
> 
>  
> +static void kvmppc_check_requests(struct kvm_vcpu *vcpu)
> +{
> +#if defined(CONFIG_KVM_E500V2) || defined(CONFIG_KVM_E500MC)
> +	if (vcpu->requests)
> +		if (kvm_check_request(KVM_REQ_TLB_FLUSH, vcpu))
> +			kvmppc_core_flush_tlb(vcpu);
> +#endif
> +}
> +
>  /*
>   * Common checks before entering the guest world.  Call with interrupts
>   * disabled.
> @@ -485,12 +494,24 @@ static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
>  			break;
>  		}
>  
> +		smp_mb();
> +		kvmppc_check_requests(vcpu);
> +

On x86 we do the requests processing while in normal preemptible
context, then do an additional check for requests != 0 during guest
entry.  This allows us to do sleepy things in request processing, and
reduces the amount of work we do with interrupts disabled.

>  		if (kvmppc_core_prepare_to_enter(vcpu)) {
>  			/* interrupts got enabled in between, so we
>  			   are back at square 1 */
>  			continue;
>  		}
>  
> +		if (vcpu->mode == EXITING_GUEST_MODE) {
> +			r = 1;
> +			break;
> +		}
> +
> +		/* Going into guest context! Yay! */
> +		vcpu->mode = IN_GUEST_MODE;
> +		smp_wmb();
> +
>  		break;
>  	}
>  
> @@ -560,6 +581,8 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
>  #endif
>  
>  	kvm_guest_exit();
> +	vcpu->mode = OUTSIDE_GUEST_MODE;
> +	smp_wmb();
>  
> +/************* MMU Notifiers *************/
> +
> +int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)
> +{
> +	/* Is this a guest page? */
> +	if (!hva_to_memslot(kvm, hva))
> +		return 0;
> +
> +	/*
> +	 * Flush all shadow tlb entries everywhere. This is slow, but
> +	 * we are 100% sure that we catch the to be unmapped page
> +	 */
> +	kvm_flush_remote_tlbs(kvm);

Wow.

> +
> +	return 0;
> +}
> +

Where do you drop the reference count when installing a page in a shadow
tlb entry?


-- 
error compiling committee.c: too many arguments to function