[PATCH v11 33/43] KVM: arm64: nv: Fold GICv3 host trapping requirements into guest setup

[Marc Zyngier]

Popular HW that is able to use NV also has a broken vgic implementation
that requires trapping.

On such HW, propagate the host trap bits into the guest's shadow
ICH_HCR_EL2 register, making sure we don't allow an L2 guest to bring
the system down.

This involves a bit of tweaking so that the emulation code correctly
poicks up the shadow state as needed, and to only partially sync
ICH_HCR_EL2 back with the guest state to capture EOIcount.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/vgic/vgic-v3-nested.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-v3-nested.c b/arch/arm64/kvm/vgic/vgic-v3-nested.c
index e4919cc82daf..b8f4dd39676c 100644
--- a/arch/arm64/kvm/vgic/vgic-v3-nested.c
+++ b/arch/arm64/kvm/vgic/vgic-v3-nested.c
@@ -168,9 +168,19 @@ void vgic_v3_create_shadow_state(struct kvm_vcpu *vcpu)
 {
 	struct vgic_v3_cpu_if *s_cpu_if = vcpu_shadow_if(vcpu);
 	struct vgic_v3_cpu_if *host_if = &vcpu->arch.vgic_cpu.vgic_v3;
+	u64 val = 0;
 	int i;
 
-	s_cpu_if->vgic_hcr = __vcpu_sys_reg(vcpu, ICH_HCR_EL2);
+	/*
+	 * If we're on a system with a broken vgic that requires
+	 * trapping, propagate the trapping requirements.
+	 *
+	 * Ah, the smell of rotten fruits...
+	 */
+	if (static_branch_unlikely(&vgic_v3_cpuif_trap))
+		val = host_if->vgic_hcr & (ICH_HCR_TALL0 | ICH_HCR_TALL1 |
+					   ICH_HCR_TC | ICH_HCR_TDIR);
+	s_cpu_if->vgic_hcr = __vcpu_sys_reg(vcpu, ICH_HCR_EL2) | val;
 	s_cpu_if->vgic_vmcr = __vcpu_sys_reg(vcpu, ICH_VMCR_EL2);
 	s_cpu_if->vgic_sre = host_if->vgic_sre;
 
@@ -203,6 +213,7 @@ void vgic_v3_load_nested(struct kvm_vcpu *vcpu)
 void vgic_v3_put_nested(struct kvm_vcpu *vcpu)
 {
 	struct vgic_v3_cpu_if *s_cpu_if = vcpu_shadow_if(vcpu);
+	u64 val;
 	int i;
 
 	__vgic_v3_save_state(s_cpu_if);
@@ -211,7 +222,10 @@ void vgic_v3_put_nested(struct kvm_vcpu *vcpu)
 	 * Translate the shadow state HW fields back to the virtual ones
 	 * before copying the shadow struct back to the nested one.
 	 */
-	__vcpu_sys_reg(vcpu, ICH_HCR_EL2) = s_cpu_if->vgic_hcr;
+	val = __vcpu_sys_reg(vcpu, ICH_HCR_EL2);
+	val &= ~ICH_HCR_EOIcount_MASK;
+	val |= (s_cpu_if->vgic_hcr & ICH_HCR_EOIcount_MASK);
+	__vcpu_sys_reg(vcpu, ICH_HCR_EL2) = val;
 	__vcpu_sys_reg(vcpu, ICH_VMCR_EL2) = s_cpu_if->vgic_vmcr;
 
 	for (i = 0; i < 4; i++) {
@@ -220,7 +234,7 @@ void vgic_v3_put_nested(struct kvm_vcpu *vcpu)
 	}
 
 	for (i = 0; i < s_cpu_if->used_lrs; i++) {
-		u64 val = __vcpu_sys_reg(vcpu, ICH_LRN(i));
+		val = __vcpu_sys_reg(vcpu, ICH_LRN(i));
 
 		val &= ~ICH_LR_STATE;
 		val |= s_cpu_if->vgic_lr[i] & ICH_LR_STATE;
-- 
2.39.2