KVM: arm64: nv: Allocate VNCR page when required

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.

Reviewed-by: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20250514103501.2225951-3-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 4a3fc11f7ecf30073626a7d7c956d8f3454cbcbb..0513f136721916b7bd52e62a64e2f5a52a8c2667 100644 (file)
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -55,6 +55,13 @@ int kvm_vcpu_init_nested(struct kvm_vcpu *vcpu)
            !cpus_have_final_cap(ARM64_HAS_HCR_NV1))
                return -EINVAL;
 
+       if (!vcpu->arch.ctxt.vncr_array)
+               vcpu->arch.ctxt.vncr_array = (u64 *)__get_free_page(GFP_KERNEL_ACCOUNT |
+                                                                   __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
@@ -85,6 +92,9 @@ 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 f82fcc614e13681960cb3379466a99b198a2fa43..965e1429b9f6e372d3e7f4fc5c7481e7cfe81cb4 100644 (file)
--- 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);
 }