Re: [RFC 23/37] KVM: s390: protvirt: Make sure prefix is always protected

[David Hildenbrand <david@xxxxxxxxxx>]

On 24.10.19 13:40, Janosch Frank wrote:
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> ---
>   arch/s390/kvm/kvm-s390.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index eddc9508c1b1..17a78774c617 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -3646,6 +3646,15 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
>   		rc = gmap_mprotect_notify(vcpu->arch.gmap,
>   					  kvm_s390_get_prefix(vcpu),
>   					  PAGE_SIZE * 2, PROT_WRITE);
> +		if (!rc && kvm_s390_pv_is_protected(vcpu->kvm)) {
> +			rc = uv_convert_to_secure(vcpu->arch.gmap,
> +						  kvm_s390_get_prefix(vcpu));
> +			WARN_ON_ONCE(rc && rc != -EEXIST);
> +			rc = uv_convert_to_secure(vcpu->arch.gmap,
> +						  kvm_s390_get_prefix(vcpu) + PAGE_SIZE);
> +			WARN_ON_ONCE(rc && rc != -EEXIST);
> +			rc = 0;
> +		}

... what if userspace reads the prefix pages just after these calls? 
validity? :/

>   		if (rc) {
>   			kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
>   			return rc;

--

Thanks,

David / dhildenb