Re: [PATCH 10/30] KVM: arm64: Introduce __pkvm_host_donate_guest()

On Tue, Jan 06, 2026 at 02:48:00PM +0000, Quentin Perret wrote:

On Monday 05 Jan 2026 at 15:49:18 (+0000), Will Deacon wrote:

quoted

+static void handle___pkvm_host_donate_guest(struct kvm_cpu_context *host_ctxt)
+{
+	DECLARE_REG(u64, pfn, host_ctxt, 1);
+	DECLARE_REG(u64, gfn, host_ctxt, 2);
+	struct pkvm_hyp_vcpu *hyp_vcpu;
+	int ret = -EINVAL;
+
+	hyp_vcpu = pkvm_get_loaded_hyp_vcpu();
+	if (!hyp_vcpu)

I guess we should check this is a protected VM here, else a malicious
host could donate pages to an np-guest. I didn't try to think through
the implications, perhaps it's fine, but it feels unecessary so I'd say
let's be restrictive here.

It's definitely harmless to add the check, but it's also hard to justify
in my opinion. Can you think of anything that can actually go wrong it
a malicious host donates memory to a non-protected guest? Generally,
I think the fewer places where we have to distinguish between a
protected and a non-protected guest in the hypervisor, the better.

Will