[PATCH v2 12/25] KVM: arm64: Enable GICv3 Group-1 sysreg trapping via command-line

[Marc Zyngier]

Now that we're able to safely handle Group-1 sysreg access, let's
give the user the opportunity to enable it by passing a specific
command-line option (vgic_v3.group1_trap).

Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
---
 virt/kvm/arm/hyp/vgic-v3-sr.c |  6 +++++-
 virt/kvm/arm/vgic/vgic-v3.c   | 11 +++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/arm/hyp/vgic-v3-sr.c b/virt/kvm/arm/hyp/vgic-v3-sr.c
index 8973bad35748..42ac9ee7650a 100644
--- a/virt/kvm/arm/hyp/vgic-v3-sr.c
+++ b/virt/kvm/arm/hyp/vgic-v3-sr.c
@@ -334,7 +334,11 @@ void __hyp_text __vgic_v3_restore_state(struct kvm_vcpu *vcpu)
 		for (i = 0; i < used_lrs; i++)
 			__gic_v3_set_lr(cpu_if->vgic_lr[i], i);
 	} else {
-		/* Always write ICH_HCR_EL2 to enable trapping */
+		/*
+                 * If we don't have any interrupt to inject, but that
+		 * trapping is enabled, write the ICH_HCR_EL2 config
+		 * anyway.
+		 */
 		if (static_branch_unlikely(&vgic_v3_cpuif_trap))
 			write_gicreg(cpu_if->vgic_hcr, ICH_HCR_EL2);
 	}
diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index fbd678bc046d..a16769276efd 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -416,6 +416,12 @@ int vgic_v3_map_resources(struct kvm *kvm)
 
 DEFINE_STATIC_KEY_FALSE(vgic_v3_cpuif_trap);
 
+static int __init early_group1_trap_cfg(char *buf)
+{
+	return strtobool(buf, &group1_trap);
+}
+early_param("vgic_v3.group1_trap", early_group1_trap_cfg);
+
 /**
  * vgic_v3_probe - probe for a GICv3 compatible interrupt controller in DT
  * @node:	pointer to the DT node
@@ -467,6 +473,11 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
 	if (kvm_vgic_global_state.vcpu_base == 0)
 		kvm_info("disabling GICv2 emulation\n");
 
+	if (group1_trap) {
+		kvm_info("GICv3 sysreg trapping enabled (reduced performance)\n");
+		static_branch_enable(&vgic_v3_cpuif_trap);
+	}
+
 	kvm_vgic_global_state.vctrl_base = NULL;
 	kvm_vgic_global_state.type = VGIC_V3;
 	kvm_vgic_global_state.max_gic_vcpus = VGIC_V3_MAX_CPUS;
-- 
2.11.0