[PATCH v4 06/15] KVM: arm64: nv: Add trap forwarding for ERET and SMC

[Marc Zyngier]

Honor the trap forwarding bits for both ERET and SMC, using a new
helper that checks for common conditions.

Reviewed-by: Joey Gouly <joey.gouly at arm.com>
Co-developed-by: Jintack Lim <jintack.lim at linaro.org>
Signed-off-by: Jintack Lim <jintack.lim at linaro.org>
Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/include/asm/kvm_nested.h |  1 +
 arch/arm64/kvm/emulate-nested.c     | 27 +++++++++++++++++++++++++++
 arch/arm64/kvm/handle_exit.c        |  7 +++++++
 3 files changed, 35 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index c77d795556e1..dbc4e3a67356 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -60,6 +60,7 @@ static inline u64 translate_ttbr0_el2_to_ttbr0_el1(u64 ttbr0)
 	return ttbr0 & ~GENMASK_ULL(63, 48);
 }
 
+extern bool forward_smc_trap(struct kvm_vcpu *vcpu);
 
 int kvm_init_nv_sysregs(struct kvm *kvm);
 
diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index 4697ba41b3a9..2d80e81ae650 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -2117,6 +2117,26 @@ bool triage_sysreg_trap(struct kvm_vcpu *vcpu, int *sr_index)
 	return true;
 }
 
+static bool forward_traps(struct kvm_vcpu *vcpu, u64 control_bit)
+{
+	bool control_bit_set;
+
+	if (!vcpu_has_nv(vcpu))
+		return false;
+
+	control_bit_set = __vcpu_sys_reg(vcpu, HCR_EL2) & control_bit;
+	if (!is_hyp_ctxt(vcpu) && control_bit_set) {
+		kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+		return true;
+	}
+	return false;
+}
+
+bool forward_smc_trap(struct kvm_vcpu *vcpu)
+{
+	return forward_traps(vcpu, HCR_TSC);
+}
+
 static u64 kvm_check_illegal_exception_return(struct kvm_vcpu *vcpu, u64 spsr)
 {
 	u64 mode = spsr & PSR_MODE_MASK;
@@ -2155,6 +2175,13 @@ void kvm_emulate_nested_eret(struct kvm_vcpu *vcpu)
 	u64 spsr, elr, mode;
 	bool direct_eret;
 
+	/*
+	 * Forward this trap to the virtual EL2 if the virtual
+	 * HCR_EL2.NV bit is set and this is coming from !EL2.
+	 */
+	if (forward_traps(vcpu, HCR_NV))
+		return;
+
 	/*
 	 * Going through the whole put/load motions is a waste of time
 	 * if this is a VHE guest hypervisor returning to its own
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 15221e481ccd..6a88ec024e2f 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -55,6 +55,13 @@ static int handle_hvc(struct kvm_vcpu *vcpu)
 
 static int handle_smc(struct kvm_vcpu *vcpu)
 {
+	/*
+	 * Forward this trapped smc instruction to the virtual EL2 if
+	 * the guest has asked for it.
+	 */
+	if (forward_smc_trap(vcpu))
+		return 1;
+
 	/*
 	 * "If an SMC instruction executed at Non-secure EL1 is
 	 * trapped to EL2 because HCR_EL2.TSC is 1, the exception is a
-- 
2.39.2