[PATCH 02/14] KVM: arm64: nv: Allocate VNCR page when required

[Marc Zyngier <maz@kernel.org>]

If running a NV guest on an ARMv8.4-NV capable system, let's
allocate an additional page that will be used by the hypervisor
to fulfill system register accesses.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/nested.c | 9 +++++++++
 arch/arm64/kvm/reset.c  | 1 +
 2 files changed, 10 insertions(+)

diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 0c9387d2f5070..952a1558f5214 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -54,6 +54,12 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
 	struct kvm_s2_mmu *tmp;
 	int num_mmus, ret = 0;
 
+	if (!vcpu->arch.ctxt.vncr_array)
+		vcpu->arch.ctxt.vncr_array = (u64 *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+
+	if (!vcpu->arch.ctxt.vncr_array)
+		return -ENOMEM;
+
 	/*
 	 * Let's treat memory allocation failures as benign: If we fail to
 	 * allocate anything, return an error and keep the allocated array
@@ -84,6 +90,9 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
 		for (int i = kvm->arch.nested_mmus_size; i < num_mmus; i++)
 			kvm_free_stage2_pgd(&kvm->arch.nested_mmus[i]);
 
+		free_page((unsigned long)vcpu->arch.ctxt.vncr_array);
+		vcpu->arch.ctxt.vncr_array = NULL;
+
 		return ret;
 	}
 
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 803e11b0dc8f5..3c48527aef360 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -158,6 +158,7 @@ void kvm_arm_vcpu_destroy(struct kvm_vcpu *vcpu)
 	if (sve_state)
 		kvm_unshare_hyp(sve_state, sve_state + vcpu_sve_state_size(vcpu));
 	kfree(sve_state);
+	free_page((unsigned long)vcpu->arch.ctxt.vncr_array);
 	kfree(vcpu->arch.ccsidr);
 }
 
-- 
2.39.2