[RFC PATCH v2 16/31] KVM: arm64: Introduce sys_reg_desc.forward_trap

[Jintack Lim]

This introduces a function prototype to determine if we need to forward
system instruction traps to the virtual EL2. The implementation of
forward_trap functions for each system instruction will be added in
later patches.

Signed-off-by: Jintack Lim <jintack.lim at linaro.org>
---
 arch/arm64/kvm/sys_regs.c | 8 ++++++++
 arch/arm64/kvm/sys_regs.h | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 541bb97..88ce172 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1661,6 +1661,14 @@ static void perform_access(struct kvm_vcpu *vcpu,
 	 */
 	BUG_ON(!r->access);
 
+	/*
+	 * Forward this trap to the virtual EL2 if the guest hypervisor has
+	 * configured to trap the current instruction.
+	 */
+	if (nested_virt_in_use(vcpu) && r->forward_trap
+	    && unlikely(r->forward_trap(vcpu)))
+		return;
+
 	/* Skip instruction if instructed so */
 	if (likely(r->access(vcpu, params, r)))
 		kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h
index 827717b..6dd4008 100644
--- a/arch/arm64/kvm/sys_regs.h
+++ b/arch/arm64/kvm/sys_regs.h
@@ -61,6 +61,12 @@ struct sys_reg_desc {
 			const struct kvm_one_reg *reg, void __user *uaddr);
 	int (*set_user)(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 			const struct kvm_one_reg *reg, void __user *uaddr);
+
+	/*
+	 * Forward the trap to the virtual EL2 if the guest hypervisor has
+	 * configured to trap the current instruction.
+	 */
+	bool (*forward_trap)(struct kvm_vcpu *vcpu);
 };
 
 static inline void print_sys_reg_instr(const struct sys_reg_params *p)
-- 
1.9.1