[PATCH 08/17] KVM: arm64: Implement HVC handling for protected guests at EL2

[Fuad Tabba <fuad.tabba@linux.dev>]

Extend kvm_handle_pvm_hvc64() to handle SMCCC_VERSION,
SMCCC_ARCH_FEATURES and the vendor hypervisor call UID at EL2, so
these queries do not reach the host. ARCH_FEATURES is mandatory from
SMCCC 1.1, the version EL2 reports: it returns SUCCESS for itself and
for SMCCC_VERSION, and NOT_SUPPORTED for anything else.

Add handle_pvm_entry_hvc64() and handle_pvm_exit_hvc64(), which
forward a protected guest's HVCs to the host and return the reply; a
later patch wires them into the per-EC dispatch tables.

Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 arch/arm64/kvm/hyp/nvhe/hyp-main.c | 28 ++++++++++++++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/pkvm.c     | 29 +++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index d4b0f69ff130c..62864db1e099a 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -4,6 +4,8 @@
  * Author: Andrew Scull <ascull@google.com>
  */
 
+#include <kvm/arm_hypercalls.h>
+
 #include <hyp/adjust_pc.h>
 #include <hyp/switch.h>
 
@@ -33,6 +35,32 @@ void __kvm_hyp_host_forward_smc(struct kvm_cpu_context *host_ctxt);
 
 typedef void (*hyp_entry_exit_handler_fn)(struct pkvm_hyp_vcpu *);
 
+static void __maybe_unused handle_pvm_entry_hvc64(struct pkvm_hyp_vcpu *hyp_vcpu)
+{
+	int i;
+
+	for (i = 0; i < 4; i++) {
+		u64 ret =
+			READ_ONCE(hyp_vcpu->host_vcpu->arch.ctxt.regs.regs[i]);
+		vcpu_set_reg(&hyp_vcpu->vcpu, i, ret);
+	}
+}
+
+static void __maybe_unused handle_pvm_exit_hvc64(struct pkvm_hyp_vcpu *hyp_vcpu)
+{
+	struct kvm_vcpu *host_vcpu = hyp_vcpu->host_vcpu;
+	int i;
+
+	WRITE_ONCE(host_vcpu->arch.fault.esr_el2,
+		   hyp_vcpu->vcpu.arch.fault.esr_el2);
+
+	/* Pass the HVC function id (r0) and its arguments. */
+	for (i = 0; i < 8; i++) {
+		WRITE_ONCE(host_vcpu->arch.ctxt.regs.regs[i],
+			   vcpu_get_reg(&hyp_vcpu->vcpu, i));
+	}
+}
+
 static void handle_vm_entry_generic(struct pkvm_hyp_vcpu *hyp_vcpu)
 {
 	vcpu_copy_flag(&hyp_vcpu->vcpu, hyp_vcpu->host_vcpu, PC_UPDATE_REQ);
diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index af334318d0a03..0fe11f95e2e26 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -1144,8 +1144,37 @@ bool kvm_handle_pvm_hvc64(struct kvm_vcpu *vcpu, u64 *exit_code)
 {
 	u64 val[4] = { SMCCC_RET_INVALID_PARAMETER };
 	bool handled = true;
+	u32 feature;
+	uuid_t uuid;
 
 	switch (smccc_get_function(vcpu)) {
+	case ARM_SMCCC_VERSION_FUNC_ID:
+		/* Nothing to be handled by the host. Go back to the guest. */
+		val[0] = ARM_SMCCC_VERSION_1_1;
+		val[1] = 0;
+		val[2] = 0;
+		val[3] = 0;
+		break;
+	case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
+		/* SUCCESS only for the architecture calls EL2 implements. */
+		feature = smccc_get_arg1(vcpu);
+		switch (feature) {
+		case ARM_SMCCC_VERSION_FUNC_ID:
+		case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
+			val[0] = SMCCC_RET_SUCCESS;
+			break;
+		default:
+			val[0] = SMCCC_RET_NOT_SUPPORTED;
+			break;
+		}
+		break;
+	case ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID:
+		uuid = ARM_SMCCC_VENDOR_HYP_UID_KVM;
+		val[0] = smccc_uuid_to_reg(&uuid, 0);
+		val[1] = smccc_uuid_to_reg(&uuid, 1);
+		val[2] = smccc_uuid_to_reg(&uuid, 2);
+		val[3] = smccc_uuid_to_reg(&uuid, 3);
+		break;
 	case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
 		val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES);
 		val[0] |= BIT(ARM_SMCCC_KVM_FUNC_HYP_MEMINFO);
-- 
2.39.5