Re: [PATCH v1 1/3] Add map/unmap ioctl and clean mappings post-guest

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 08.03.26 um 04:04 schrieb Douglas Freimuth:
> Fencing of Fast Inject in Secure Execution environments is enabled in
> this patch by not mapping adapter indicator pages. In Secure Execution
[...]

> @@ -2477,14 +2572,28 @@ static int modify_io_adapter(struct kvm_device *dev,
>   		if (ret > 0)
>   			ret = 0;
>   		break;
> -	/*
> -	 * The following operations are no longer needed and therefore no-ops.
> -	 * The gpa to hva translation is done when an IRQ route is set up. The
> -	 * set_irq code uses get_user_pages_remote() to do the actual write.
> -	 */
>   	case KVM_S390_IO_ADAPTER_MAP:
>   	case KVM_S390_IO_ADAPTER_UNMAP:
> -		ret = 0;
> +		mutex_lock(&dev->kvm->lock);
> +		if (kvm_s390_pv_is_protected(dev->kvm)) {
> +			mutex_unlock(&dev->kvm->lock);
> +			break;
> +		}


I guess this works for a well behaving userspaces, but a bad QEMU could in theory
not do the unmap on switch to secure.
Shall we maybe do -EINVAL on KVM_PV_ENABLE if there are still mapping left, or
to make it easier for userspace remove the old ADAPTER maps?