KVM: arm64: Add basic hooks for injecting exceptions from EL2

Add the basic infrastructure to describe injection of exceptions
into a guest. So far, nothing uses this code path.
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/include/asm/kvm_host.h

@@ -407,7 +407,31 @@ struct kvm_vcpu_arch {
 #define KVM_ARM64_GUEST_HAS_SVE		(1 << 5) /* SVE exposed to guest */
 #define KVM_ARM64_VCPU_SVE_FINALIZED	(1 << 6) /* SVE config completed */
 #define KVM_ARM64_GUEST_HAS_PTRAUTH	(1 << 7) /* PTRAUTH exposed to guest */
-#define KVM_ARM64_INCREMENT_PC		(1 << 8) /* Increment PC */
+#define KVM_ARM64_PENDING_EXCEPTION	(1 << 8) /* Exception pending */
+#define KVM_ARM64_EXCEPT_MASK		(7 << 9) /* Target EL/MODE */
+
+/*
+ * When KVM_ARM64_PENDING_EXCEPTION is set, KVM_ARM64_EXCEPT_MASK can
+ * take the following values:
+ *
+ * For AArch32 EL1:
+ */
+#define KVM_ARM64_EXCEPT_AA32_UND	(0 << 9)
+#define KVM_ARM64_EXCEPT_AA32_IABT	(1 << 9)
+#define KVM_ARM64_EXCEPT_AA32_DABT	(2 << 9)
+/* For AArch64: */
+#define KVM_ARM64_EXCEPT_AA64_ELx_SYNC	(0 << 9)
+#define KVM_ARM64_EXCEPT_AA64_ELx_IRQ	(1 << 9)
+#define KVM_ARM64_EXCEPT_AA64_ELx_FIQ	(2 << 9)
+#define KVM_ARM64_EXCEPT_AA64_ELx_SERR	(3 << 9)
+#define KVM_ARM64_EXCEPT_AA64_EL1	(0 << 11)
+#define KVM_ARM64_EXCEPT_AA64_EL2	(1 << 11)
+
+/*
+ * Overlaps with KVM_ARM64_EXCEPT_MASK on purpose so that it can't be
+ * set together with an exception...
+ */
+#define KVM_ARM64_INCREMENT_PC		(1 << 9) /* Increment PC */
 
 #define vcpu_has_sve(vcpu) (system_supports_sve() &&			\
 			    ((vcpu)->arch.flags & KVM_ARM64_GUEST_HAS_SVE))

arch/arm64/kvm/hyp/exception.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Fault injection for both 32 and 64bit guests.
+ *
+ * Copyright (C) 2012,2013 - ARM Ltd
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * Based on arch/arm/kvm/emulate.c
+ * Copyright (C) 2012 - Virtual Open Systems and Columbia University
+ * Author: Christoffer Dall <c.dall@virtualopensystems.com>
+ */
+
+#include <hyp/adjust_pc.h>
+
+void kvm_inject_exception(struct kvm_vcpu *vcpu)
+{
+}

arch/arm64/kvm/hyp/include/hyp/adjust_pc.h

@@ -13,6 +13,8 @@
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_host.h>
 
+void kvm_inject_exception(struct kvm_vcpu *vcpu);
+
 static inline void kvm_skip_instr(struct kvm_vcpu *vcpu)
 {
 	if (vcpu_mode_is_32bit(vcpu)) {
@@ -43,11 +45,15 @@ static inline void __kvm_skip_instr(struct kvm_vcpu *vcpu)
 
 /*
  * Adjust the guest PC on entry, depending on flags provided by EL1
- * for the purpose of emulation (MMIO, sysreg).
+ * for the purpose of emulation (MMIO, sysreg) or exception injection.
  */
 static inline void __adjust_pc(struct kvm_vcpu *vcpu)
 {
-	if (vcpu->arch.flags & KVM_ARM64_INCREMENT_PC) {
+	if (vcpu->arch.flags & KVM_ARM64_PENDING_EXCEPTION) {
+		kvm_inject_exception(vcpu);
+		vcpu->arch.flags &= ~(KVM_ARM64_PENDING_EXCEPTION |
+				      KVM_ARM64_EXCEPT_MASK);
+	} else 	if (vcpu->arch.flags & KVM_ARM64_INCREMENT_PC) {
 		kvm_skip_instr(vcpu);
 		vcpu->arch.flags &= ~KVM_ARM64_INCREMENT_PC;
 	}

arch/arm64/kvm/hyp/nvhe/Makefile

@@ -8,7 +8,7 @@ ccflags-y := -D__KVM_NVHE_HYPERVISOR__
 
 obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o hyp-main.o
 obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
-	 ../fpsimd.o ../hyp-entry.o
+	 ../fpsimd.o ../hyp-entry.o ../exception.o
 
 ##
 ## Build rules for compiling nVHE hyp code

arch/arm64/kvm/hyp/vhe/Makefile

@@ -8,4 +8,4 @@ ccflags-y := -D__KVM_VHE_HYPERVISOR__
 
 obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o
 obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
-	 ../fpsimd.o ../hyp-entry.o
+	 ../fpsimd.o ../hyp-entry.o ../exception.o