[v2,08/23] KVM: arm64: Plug FEAT_GCS handling

Commit Message

Marc Zyngier March 10, 2025, 12:24 p.m. UTC

We don't seem to be handling the GCS-specific exception class.
Handle it by delivering an UNDEF to the guest, and populate the
relevant trap bits.

Signed-off-by: Marc Zyngier <[e-mail]>
---
 arch/arm64/kvm/handle_exit.c | 11 +++++++++++
 arch/arm64/kvm/sys_regs.c    |  8 ++++++++
 2 files changed, 19 insertions(+)

Patch

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index b2d11cd0447c1..bf08c44491b4a 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -294,6 +294,16 @@  static int handle_svc(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
+static int kvm_handle_gcs(struct kvm_vcpu *vcpu)
+{
+	/* We don't expect GCS, so treat it with contempt */
+	if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, GCS, IMP))
+		WARN_ON_ONCE(1);
+
+	kvm_inject_undefined(vcpu);
+	return 1;
+}
+
 static int handle_other(struct kvm_vcpu *vcpu)
 {
 	bool is_l2 = vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu);
@@ -376,6 +386,7 @@  static exit_handle_fn arm_exit_handlers[] = {
 	[ESR_ELx_EC_BRK64]	= kvm_handle_guest_debug,
 	[ESR_ELx_EC_FP_ASIMD]	= kvm_handle_fpasimd,
 	[ESR_ELx_EC_PAC]	= kvm_handle_ptrauth,
+	[ESR_ELx_EC_GCS]	= kvm_handle_gcs,
 };
 
 static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 18721c773475d..2ecd0d51a2dae 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -5056,6 +5056,14 @@  void kvm_calculate_traps(struct kvm_vcpu *vcpu)
 						HFGITR_EL2_nBRBIALL);
 	}
 
+	if (!kvm_has_feat(kvm, ID_AA64PFR1_EL1, GCS, IMP)) {
+		kvm->arch.fgu[HFGxTR_GROUP] |= (HFGxTR_EL2_nGCS_EL0 |
+						HFGxTR_EL2_nGCS_EL1);
+		kvm->arch.fgu[HFGITR_GROUP] |= (HFGITR_EL2_nGCSPUSHM_EL1 |
+						HFGITR_EL2_nGCSSTR_EL1 |
+						HFGITR_EL2_nGCSEPP);
+	}
+
 	set_bit(KVM_ARCH_FLAG_FGU_INITIALIZED, &kvm->arch.flags);
 out:
 	mutex_unlock(&kvm->arch.config_lock);