KVM: arm64: Initialize the hypervisor's VM state at EL2

Do not trust the state of the VM as provided by the host when
initializing the hypervisor's view of the VM sate. Initialize it
instead at EL2 to a known good and safe state, as pKVM already
does with hypervisor VCPU states.

Signed-off-by: Fuad Tabba <tabba@google.com>
Link: https://lore.kernel.org/r/20241018074833.2563674-4-tabba@google.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

1 files changed, 77 insertions, 0 deletions

diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index 869955e551a0..954df57a935f 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -6,6 +6,9 @@
 
 #include <linux/kvm_host.h>
 #include <linux/mm.h>
+
+#include <asm/kvm_emulate.h>
+
 #include <nvhe/fixed_config.h>
 #include <nvhe/mem_protect.h>
 #include <nvhe/memory.h>
@@ -289,6 +292,65 @@ void pkvm_put_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu)
 	hyp_spin_unlock(&vm_table_lock);
 }
 
+static void pkvm_init_features_from_host(struct pkvm_hyp_vm *hyp_vm, const struct kvm *host_kvm)
+{
+	struct kvm *kvm = &hyp_vm->kvm;
+	DECLARE_BITMAP(allowed_features, KVM_VCPU_MAX_FEATURES);
+
+	/* No restrictions for non-protected VMs. */
+	if (!kvm_vm_is_protected(kvm)) {
+		bitmap_copy(kvm->arch.vcpu_features,
+			    host_kvm->arch.vcpu_features,
+			    KVM_VCPU_MAX_FEATURES);
+		return;
+	}
+
+	bitmap_zero(allowed_features, KVM_VCPU_MAX_FEATURES);
+
+	/*
+	 * For protected VMs, always allow:
+	 * - CPU starting in poweroff state
+	 * - PSCI v0.2
+	 */
+	set_bit(KVM_ARM_VCPU_POWER_OFF, allowed_features);
+	set_bit(KVM_ARM_VCPU_PSCI_0_2, allowed_features);
+
+	/*
+	 * Check if remaining features are allowed:
+	 * - Performance Monitoring
+	 * - Scalable Vectors
+	 * - Pointer Authentication
+	 */
+	if (FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer), PVM_ID_AA64DFR0_ALLOW))
+		set_bit(KVM_ARM_VCPU_PMU_V3, allowed_features);
+
+	if (FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_SVE), PVM_ID_AA64PFR0_ALLOW))
+		set_bit(KVM_ARM_VCPU_SVE, allowed_features);
+
+	if (FIELD_GET(ARM64_FEATURE_MASK(ID_AA64ISAR1_EL1_API), PVM_ID_AA64ISAR1_RESTRICT_UNSIGNED) &&
+	    FIELD_GET(ARM64_FEATURE_MASK(ID_AA64ISAR1_EL1_APA), PVM_ID_AA64ISAR1_RESTRICT_UNSIGNED))
+		set_bit(KVM_ARM_VCPU_PTRAUTH_ADDRESS, allowed_features);
+
+	if (FIELD_GET(ARM64_FEATURE_MASK(ID_AA64ISAR1_EL1_GPI), PVM_ID_AA64ISAR1_ALLOW) &&
+	    FIELD_GET(ARM64_FEATURE_MASK(ID_AA64ISAR1_EL1_GPA), PVM_ID_AA64ISAR1_ALLOW))
+		set_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, allowed_features);
+
+	bitmap_and(kvm->arch.vcpu_features, host_kvm->arch.vcpu_features,
+		   allowed_features, KVM_VCPU_MAX_FEATURES);
+}
+
+static void pkvm_vcpu_init_ptrauth(struct pkvm_hyp_vcpu *hyp_vcpu)
+{
+	struct kvm_vcpu *vcpu = &hyp_vcpu->vcpu;
+
+	if (vcpu_has_feature(vcpu, KVM_ARM_VCPU_PTRAUTH_ADDRESS) ||
+	    vcpu_has_feature(vcpu, KVM_ARM_VCPU_PTRAUTH_GENERIC)) {
+		kvm_vcpu_enable_ptrauth(vcpu);
+	} else {
+		vcpu_clear_flag(&hyp_vcpu->vcpu, GUEST_HAS_PTRAUTH);
+	}
+}
+
 static void unpin_host_vcpu(struct kvm_vcpu *host_vcpu)
 {
 	if (host_vcpu)
@@ -310,6 +372,18 @@ static void init_pkvm_hyp_vm(struct kvm *host_kvm, struct pkvm_hyp_vm *hyp_vm,
 	hyp_vm->host_kvm = host_kvm;
 	hyp_vm->kvm.created_vcpus = nr_vcpus;
 	hyp_vm->kvm.arch.mmu.vtcr = host_mmu.arch.mmu.vtcr;
+	hyp_vm->kvm.arch.pkvm.enabled = READ_ONCE(host_kvm->arch.pkvm.enabled);
+	pkvm_init_features_from_host(hyp_vm, host_kvm);
+}
+
+static void pkvm_vcpu_init_sve(struct pkvm_hyp_vcpu *hyp_vcpu, struct kvm_vcpu *host_vcpu)
+{
+	struct kvm_vcpu *vcpu = &hyp_vcpu->vcpu;
+
+	if (!vcpu_has_feature(vcpu, KVM_ARM_VCPU_SVE)) {
+		vcpu_clear_flag(vcpu, GUEST_HAS_SVE);
+		vcpu_clear_flag(vcpu, VCPU_SVE_FINALIZED);
+	}
 }
 
 static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu,
@@ -335,7 +409,10 @@ static int init_pkvm_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu,
 
 	hyp_vcpu->vcpu.arch.hw_mmu = &hyp_vm->kvm.arch.mmu;
 	hyp_vcpu->vcpu.arch.cflags = READ_ONCE(host_vcpu->arch.cflags);
+	hyp_vcpu->vcpu.arch.mp_state.mp_state = KVM_MP_STATE_STOPPED;
 
+	pkvm_vcpu_init_sve(hyp_vcpu, host_vcpu);
+	pkvm_vcpu_init_ptrauth(hyp_vcpu);
 	pkvm_vcpu_init_traps(&hyp_vcpu->vcpu);
 done:
 	if (ret)