[RFC 18/55] KVM: arm64: Forward traps due to HCR_EL2.NV1 bit to the guest hypervisor

[Jintack Lim]

Forward ELR_EL1, SPSR_EL1 and VBAR_EL1 traps to the guest hypervisor if
it has set the NV1 bit to the virtual HCR_EL2. The guest hypervisor
would set this NV1 bit to run a hypervisor in its VM (i.e. another level
of nested hypervisor).

Signed-off-by: Jintack Lim <jintack at cs.columbia.edu>
---
 arch/arm64/include/asm/kvm_arm.h |  1 +
 arch/arm64/kvm/sys_regs.c        | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 2a2752b..feded61 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -23,6 +23,7 @@
 #include <asm/types.h>
 
 /* Hyp Configuration Register (HCR) bits */
+#define HCR_NV1		(UL(1) << 43)
 #define HCR_E2H		(UL(1) << 34)
 #define HCR_ID		(UL(1) << 33)
 #define HCR_CD		(UL(1) << 32)
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 19d6a6e..59f9cc6 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -906,10 +906,21 @@ static inline void access_rw(struct sys_reg_params *p, u64 *sysreg)
 		*sysreg = p->regval;
 }
 
+static bool forward_nv1_traps(struct kvm_vcpu *vcpu, struct sys_reg_params *p)
+{
+	if (!vcpu_mode_el2(vcpu) && (vcpu_el2_reg(vcpu, HCR_EL2) & HCR_NV1))
+		return true;
+
+	return false;
+}
+
 static bool access_elr(struct kvm_vcpu *vcpu,
 		struct sys_reg_params *p,
 		const struct sys_reg_desc *r)
 {
+	if (forward_nv1_traps(vcpu, p))
+		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+
 	access_rw(p, &vcpu->arch.ctxt.gp_regs.elr_el1);
 	return true;
 }
@@ -918,6 +929,9 @@ static bool access_spsr(struct kvm_vcpu *vcpu,
 		struct sys_reg_params *p,
 		const struct sys_reg_desc *r)
 {
+	if (forward_nv1_traps(vcpu, p))
+		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+
 	access_rw(p, &vcpu->arch.ctxt.gp_regs.spsr[KVM_SPSR_EL1]);
 	return true;
 }
@@ -926,6 +940,9 @@ static bool access_vbar(struct kvm_vcpu *vcpu,
 		struct sys_reg_params *p,
 		const struct sys_reg_desc *r)
 {
+	if (forward_nv1_traps(vcpu, p))
+		return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
+
 	access_rw(p, &vcpu_sys_reg(vcpu, r->reg));
 	return true;
 }
-- 
1.9.1