[PATCH v16 35/45] KVM: arm64: CCA: Support RSI_HOST_CALL

[Steven Price <steven.price@arm.com>]

From: Joey Gouly <joey.gouly@arm.com>

Realm VMs can talk to the hypervisor using the RSI_HOST_CALL SMC. The
RMM forwards this to the host and KVM handles them as regular
hypercalls.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
Changes since v15:
 * Adapt to new exit handling.
Changes since v7:
 * Avoid turning a negative return from kvm_smccc_call_handler() into a
   error response to the guest. Instead propagate the error back to user
   space.
Changes since v4:
 * Setting GPRS is now done by kvm_rec_enter() rather than
   rec_exit_host_call() (see previous patch - arm64: RME: Handle realm
   enter/exit). This fixes a bug where the registers set by user space
   were being ignored.
---
 arch/arm64/kvm/rmi-exit.c | 1 +
 arch/arm64/kvm/rmi.c      | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/arm64/kvm/rmi-exit.c b/arch/arm64/kvm/rmi-exit.c
index 1749cde2edff..7cde820bb77b 100644
--- a/arch/arm64/kvm/rmi-exit.c
+++ b/arch/arm64/kvm/rmi-exit.c
@@ -164,6 +164,7 @@ int kvm_rec_exit(struct kvm_vcpu *vcpu, int rec_run_ret)
 	case RMI_EXIT_SERROR:
 		return ARM_EXCEPTION_EL1_SERROR;
 	case RMI_EXIT_PSCI:
+	case RMI_EXIT_HOST_CALL:
 		rec_exit_hvc(vcpu);
 		kvm_make_request(KVM_REQ_RMI, vcpu);
 		return ARM_EXCEPTION_TRAP;
diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
index 3f31ad25680f..904df7c7245d 100644
--- a/arch/arm64/kvm/rmi.c
+++ b/arch/arm64/kvm/rmi.c
@@ -1203,6 +1203,10 @@ int kvm_rec_handle_request(struct kvm_vcpu *vcpu)
 		return kvm_rec_complete_psci(vcpu);
 	case RMI_EXIT_RIPAS_CHANGE:
 		return kvm_complete_ripas_change(vcpu);
+	case RMI_EXIT_HOST_CALL:
+		for (int i = 0; i < REC_RUN_GPRS; i++)
+			rec->run->enter.gprs[i] = vcpu_get_reg(vcpu, i);
+		break;
 	default:
 		KVM_BUG(1, vcpu->kvm, "Unhandled realm exit_reason");
 		return -ENXIO;
-- 
2.43.0