[PATCH v6 61/64] KVM: arm64: nv: Allocate VNCR page when required

[Marc Zyngier <maz@xxxxxxxxxx>]

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@xxxxxxxxxx>
---
 arch/arm64/include/asm/kvm_host.h |  3 ++-
 arch/arm64/kvm/nested.c           | 10 ++++++++++
 arch/arm64/kvm/reset.c            |  1 +
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 15bbe8ccdefa..5d69992106aa 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -568,7 +568,8 @@ struct kvm_vcpu_arch {
  */
 static inline u64 *__ctxt_sys_reg(const struct kvm_cpu_context *ctxt, int r)
 {
-	if (unlikely(r >= __VNCR_START__ && ctxt->vncr_array))
+	if (unlikely(cpus_have_final_cap(ARM64_HAS_ENHANCED_NESTED_VIRT) &&
+		     r >= __VNCR_START__ && ctxt->vncr_array))
 		return &ctxt->vncr_array[r - __VNCR_START__];
 
 	return (u64 *)&ctxt->sys_regs[r];
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 8e99690cdde1..bbdd4633e665 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -35,6 +35,14 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
 	if (!cpus_have_final_cap(ARM64_HAS_NESTED_VIRT))
 		return -EINVAL;
 
+	if (cpus_have_final_cap(ARM64_HAS_ENHANCED_NESTED_VIRT)) {
+		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;
+	}
+
 	mutex_lock(&kvm->lock);
 
 	/*
@@ -64,6 +72,8 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
 		    kvm_init_stage2_mmu(kvm, &tmp[num_mmus - 2])) {
 			kvm_free_stage2_pgd(&tmp[num_mmus - 1]);
 			kvm_free_stage2_pgd(&tmp[num_mmus - 2]);
+			free_page((unsigned long)vcpu->arch.ctxt.vncr_array);
+			vcpu->arch.ctxt.vncr_array = NULL;
 		} else {
 			kvm->arch.nested_mmus_size = num_mmus;
 			ret = 0;
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index d19a9aad2d85..f59c00fb53cc 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -161,6 +161,7 @@ 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);
 }
 
 static void kvm_vcpu_reset_sve(struct kvm_vcpu *vcpu)
-- 
2.30.2