KVM: arm64: Don't WARN from __pkvm_host_share_guest()

We currently WARN() if the host attempts to share a page that is not in
an acceptable state with a guest. This isn't strictly necessary and
makes testing much harder, so drop the WARN and make sure to propage the
error code instead.

Signed-off-by: Quentin Perret <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Marc Zyngier <[email protected]>

Author: Quentin Perret

arch/arm64/kvm/hyp/nvhe/mem_protect.c

@@ -919,7 +919,6 @@ int __pkvm_host_share_guest(u64 pfn, u64 gfn, struct pkvm_hyp_vcpu *vcpu,
 		if (page->host_share_guest_count)
 			break;
 		/* Only host to np-guest multi-sharing is tolerated */
-		WARN_ON(1);
 		fallthrough;
 	default:
 		ret = -EPERM;