KVM: arm64: vgic-v3: Add hook to handle guest GICv3 sysreg accesses at EL2

In order to start handling guest access to GICv3 system registers,
let's add a hook that will get called when we trap a system register
access. This is gated by a new static key (vgic_v3_cpuif_trap).
Tested-by: Alexander Graf <agraf@suse.de>
Acked-by: David Daney <david.daney@cavium.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>

arch/arm64/include/asm/kvm_hyp.h

@@ -127,6 +127,7 @@ int __vgic_v2_perform_cpuif_access(struct kvm_vcpu *vcpu);
 
 void __vgic_v3_save_state(struct kvm_vcpu *vcpu);
 void __vgic_v3_restore_state(struct kvm_vcpu *vcpu);
+int __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu);
 
 void __timer_save_state(struct kvm_vcpu *vcpu);
 void __timer_restore_state(struct kvm_vcpu *vcpu);

arch/arm64/kvm/hyp/switch.c

@@ -350,6 +350,20 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
 		}
 	}
 
+	if (static_branch_unlikely(&vgic_v3_cpuif_trap) &&
+	    exit_code == ARM_EXCEPTION_TRAP &&
+	    (kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_SYS64 ||
+	     kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_CP15_32)) {
+		int ret = __vgic_v3_perform_cpuif_access(vcpu);
+
+		if (ret == 1) {
+			__skip_instr(vcpu);
+			goto again;
+		}
+
+		/* 0 falls through to be handled out of EL2 */
+	}
+
 	fp_enabled = __fpsimd_enabled();
 
 	__sysreg_save_guest_state(guest_ctxt);

include/kvm/arm_vgic.h

@@ -292,6 +292,7 @@ struct vgic_cpu {
 };
 
 extern struct static_key_false vgic_v2_cpuif_trap;
+extern struct static_key_false vgic_v3_cpuif_trap;
 
 int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write);
 void kvm_vgic_early_init(struct kvm *kvm);

virt/kvm/arm/hyp/vgic-v3-sr.c

@@ -19,6 +19,7 @@
 #include <linux/irqchip/arm-gic-v3.h>
 #include <linux/kvm_host.h>
 
+#include <asm/kvm_emulate.h>
 #include <asm/kvm_hyp.h>
 
 #define vtr_to_max_lr_idx(v)		((v) & 0xf)
@@ -371,3 +372,40 @@ void __hyp_text __vgic_v3_write_vmcr(u32 vmcr)
 {
 	write_gicreg(vmcr, ICH_VMCR_EL2);
 }
+
+#ifdef CONFIG_ARM64
+
+int __hyp_text __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu)
+{
+	int rt;
+	u32 esr;
+	u32 vmcr;
+	void (*fn)(struct kvm_vcpu *, u32, int);
+	bool is_read;
+	u32 sysreg;
+
+	esr = kvm_vcpu_get_hsr(vcpu);
+	if (vcpu_mode_is_32bit(vcpu)) {
+		if (!kvm_condition_valid(vcpu))
+			return 1;
+
+		sysreg = esr_cp15_to_sysreg(esr);
+	} else {
+		sysreg = esr_sys64_to_sysreg(esr);
+	}
+
+	is_read = (esr & ESR_ELx_SYS64_ISS_DIR_MASK) == ESR_ELx_SYS64_ISS_DIR_READ;
+
+	switch (sysreg) {
+	default:
+		return 0;
+	}
+
+	vmcr = __vgic_v3_read_vmcr();
+	rt = kvm_vcpu_sys_get_rt(vcpu);
+	fn(vcpu, vmcr, rt);
+
+	return 1;
+}
+
+#endif

virt/kvm/arm/vgic/vgic-v3.c

@@ -429,6 +429,8 @@ int vgic_v3_map_resources(struct kvm *kvm)
 	return ret;
 }
 
+DEFINE_STATIC_KEY_FALSE(vgic_v3_cpuif_trap);
+
 /**
  * vgic_v3_probe - probe for a GICv3 compatible interrupt controller in DT
  * @node:	pointer to the DT node