From: Jintack Lim <jintack....@linaro.org>

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....@linaro.org>
Signed-off-by: Marc Zyngier <m...@kernel.org>
---
 arch/arm64/kvm/sys_regs.c | 9 +++++++++
 arch/arm64/kvm/sys_regs.h | 6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 364020afc17c..fae3f4a70eeb 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -25,6 +25,7 @@
 #include <asm/kvm_host.h>
 #include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_nested.h>
 #include <asm/perf_event.h>
 #include <asm/sysreg.h>
 
@@ -2491,6 +2492,14 @@ 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 5a6fc30f5989..65e736f7103a 100644
--- a/arch/arm64/kvm/sys_regs.h
+++ b/arch/arm64/kvm/sys_regs.h
@@ -54,6 +54,12 @@ struct sys_reg_desc {
        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);
+
        /* Return mask of REG_* runtime visibility overrides */
        unsigned int (*visibility)(const struct kvm_vcpu *vcpu,
                                   const struct sys_reg_desc *rd);
-- 
2.20.1

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