KVM: arm64: vgic-v3: Enable trapping of Group-1 system registers

In order to be able to trap Group-1 GICv3 system registers, we need to
set ICH_HCR_EL2.TALL1 before entering the guest. This is conditionally
done after having restored the guest's state, and cleared on exit.

Tested-by: Alexander Graf <agraf@suse.de>
Acked-by: David Daney <david.daney@cavium.com>
Acked-by: Christoffer Dall <cdall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>

include/linux/irqchip/arm-gic-v3.h

@@ -417,6 +417,7 @@
 
 #define ICH_HCR_EN			(1 << 0)
 #define ICH_HCR_UIE			(1 << 1)
+#define ICH_HCR_TALL1			(1 << 12)
 #define ICH_HCR_EOIcount_SHIFT		27
 #define ICH_HCR_EOIcount_MASK		(0x1f << ICH_HCR_EOIcount_SHIFT)
 

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

@@ -258,6 +258,9 @@ void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu)
 			cpu_if->vgic_ap1r[0] = __vgic_v3_read_ap1rn(0);
 		}
 	} else {
+		if (static_branch_unlikely(&vgic_v3_cpuif_trap))
+			write_gicreg(0, ICH_HCR_EL2);
+
 		cpu_if->vgic_elrsr = 0xffff;
 		cpu_if->vgic_ap0r[0] = 0;
 		cpu_if->vgic_ap0r[1] = 0;
@@ -330,6 +333,14 @@ 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 {
+		/*
+		 * If we need to trap system registers, we must write
+		 * ICH_HCR_EL2 anyway, even if no interrupts are being
+		 * injected,
+		 */
+		if (static_branch_unlikely(&vgic_v3_cpuif_trap))
+			write_gicreg(cpu_if->vgic_hcr, ICH_HCR_EL2);
 	}
 
 	/*

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

@@ -21,6 +21,8 @@
 
 #include "vgic.h"
 
+static bool group1_trap;
+
 void vgic_v3_set_underflow(struct kvm_vcpu *vcpu)
 {
 	struct vgic_v3_cpu_if *cpuif = &vcpu->arch.vgic_cpu.vgic_v3;
@@ -258,6 +260,8 @@ void vgic_v3_enable(struct kvm_vcpu *vcpu)
 
 	/* Get the show on the road... */
 	vgic_v3->vgic_hcr = ICH_HCR_EN;
+	if (group1_trap)
+		vgic_v3->vgic_hcr |= ICH_HCR_TALL1;
 }
 
 int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq)