From: Jintack Lim <redacted>

Forward exceptions due to WFI or WFE instructions to the virtual EL2 if
they are not coming from the virtual EL2 and virtual HCR_EL2.TWX is set.

Signed-off-by: Jintack Lim <redacted>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_nested.h |  2 ++
 arch/arm64/kvm/Makefile             |  2 +-
 arch/arm64/kvm/handle_exit.c        | 11 ++++++++++-
 arch/arm64/kvm/nested.c             | 28 ++++++++++++++++++++++++++++
 4 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 arch/arm64/kvm/nested.c

diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index 5a85be6d8eb3..79d382fa02ea 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h

@@ -65,4 +65,6 @@ static inline u64 translate_cnthctl_el2_to_cntkctl_el1(u64 cnthctl)
 		(cnthctl & (CNTHCTL_EVNTI | CNTHCTL_EVNTDIR | CNTHCTL_EVNTEN)));
 }
 
+int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe);
+
 #endif /* __ARM64_KVM_NESTED_H */

diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index b67c4ebd72b1..dbaf42ff65f1 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile

@@ -14,7 +14,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
 	 inject_fault.o va_layout.o handle_exit.o \
 	 guest.o debug.o reset.o sys_regs.o \
 	 vgic-sys-reg-v3.o fpsimd.o pmu.o pkvm.o \
-	 arch_timer.o trng.o emulate-nested.o \
+	 arch_timer.o trng.o emulate-nested.o nested.o \
 	 vgic/vgic.o vgic/vgic-init.o \
 	 vgic/vgic-irqfd.o vgic/vgic-v2.o \
 	 vgic/vgic-v3.o vgic/vgic-v4.o \

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 0cedef6e0d80..a1b1bbf3d598 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c

@@ -119,7 +119,16 @@ static int handle_no_fpsimd(struct kvm_vcpu *vcpu)
  */
 static int kvm_handle_wfx(struct kvm_vcpu *vcpu)
 {
-	if (kvm_vcpu_get_esr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
+	bool is_wfe = !!(kvm_vcpu_get_esr(vcpu) & ESR_ELx_WFx_ISS_WFE);
+
+	if (vcpu_has_nv(vcpu)) {
+		int ret = handle_wfx_nested(vcpu, is_wfe);
+
+		if (ret != -EINVAL)
+			return ret;

+	}
+
+	if (is_wfe) {
 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
 		vcpu->stat.wfe_exit_stat++;
 		kvm_vcpu_on_spin(vcpu, vcpu_mode_priv(vcpu));

diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
new file mode 100644
index 000000000000..5e1104f8e765
--- /dev/null
+++ b/arch/arm64/kvm/nested.c

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2017 - Columbia University and Linaro Ltd.
+ * Author: Jintack Lim <jintack.lim@linaro.org>
+ */
+
+#include <linux/kvm.h>
+#include <linux/kvm_host.h>
+
+#include <asm/kvm_emulate.h>
+
+/*
+ * Inject wfx to the virtual EL2 if this is not from the virtual EL2 and
+ * the virtual HCR_EL2.TWX is set. Otherwise, let the host hypervisor
+ * handle this.
+ */
+int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe)
+{
+	u64 hcr_el2 = __vcpu_sys_reg(vcpu, HCR_EL2);
+
+	if (vcpu_is_el2(vcpu))
+		return -EINVAL;
+
+	if ((is_wfe && (hcr_el2 & HCR_TWE)) || (!is_wfe && (hcr_el2 & HCR_TWI)))
+		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_esr(vcpu));
+
+	return -EINVAL;
+}

-- 
2.30.2