[PATCH 4/4] KVM: arm64: vgic-v3: Advertise GICR_CTLR.{IR, CES} as a new GICD_IIDR revision

[Marc Zyngier]

Since adversising GICR_CTLR.{IC,CES} is directly observable from
a guest, we need to make it selectable from userspace.

For that, bump the default GICD_IIDR revision and let userspace
downgrade it to the previous default. For GICv2, the two distributor
revisions are strictly equivalent.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/vgic/vgic-init.c    |  7 ++++++-
 arch/arm64/kvm/vgic/vgic-mmio-v2.c | 18 +++++++++++++++---
 arch/arm64/kvm/vgic/vgic-mmio-v3.c | 23 +++++++++++++++++++++--
 include/kvm/arm_vgic.h             |  3 +++
 4 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index fc00304fe7d8..f84e04f334c6 100644
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -319,7 +319,12 @@ int vgic_init(struct kvm *kvm)
 
 	vgic_debug_init(kvm);
 
-	dist->implementation_rev = 2;
+	/*
+	 * If userspace didn't set the GIC implementation revision,
+	 * default to the latest and greatest. You know want it.
+	 */
+	if (!dist->implementation_rev)
+		dist->implementation_rev = KVM_VGIC_IMP_REV_LATEST;
 	dist->initialized = true;
 
 out:
diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v2.c b/arch/arm64/kvm/vgic/vgic-mmio-v2.c
index 12e4c223e6b8..f2246c4ca812 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v2.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v2.c
@@ -73,9 +73,13 @@ static int vgic_mmio_uaccess_write_v2_misc(struct kvm_vcpu *vcpu,
 					   gpa_t addr, unsigned int len,
 					   unsigned long val)
 {
+	struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
+	u32 reg;
+
 	switch (addr & 0x0c) {
 	case GIC_DIST_IIDR:
-		if (val != vgic_mmio_read_v2_misc(vcpu, addr, len))
+		reg = vgic_mmio_read_v2_misc(vcpu, addr, len);
+		if ((reg ^ val) & ~GICD_IIDR_REVISION_MASK)
 			return -EINVAL;
 
 		/*
@@ -87,8 +91,16 @@ static int vgic_mmio_uaccess_write_v2_misc(struct kvm_vcpu *vcpu,
 		 * migration from old kernels to new kernels with legacy
 		 * userspace.
 		 */
-		vcpu->kvm->arch.vgic.v2_groups_user_writable = true;
-		return 0;
+		reg = FIELD_GET(GICD_IIDR_REVISION_MASK, reg);
+		switch (reg) {
+		case KVM_VGIC_IMP_REV_2:
+		case KVM_VGIC_IMP_REV_3:
+			dist->v2_groups_user_writable = true;
+			dist->implementation_rev = reg;
+			return 0;
+		default:
+			return -EINVAL;
+		}
 	}
 
 	vgic_mmio_write_v2_misc(vcpu, addr, len, val);
diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
index a6be403996c6..4c8e4f83e3d1 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
@@ -155,13 +155,27 @@ static int vgic_mmio_uaccess_write_v3_misc(struct kvm_vcpu *vcpu,
 					   unsigned long val)
 {
 	struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
+	u32 reg;
 
 	switch (addr & 0x0c) {
 	case GICD_TYPER2:
-	case GICD_IIDR:
 		if (val != vgic_mmio_read_v3_misc(vcpu, addr, len))
 			return -EINVAL;
 		return 0;
+	case GICD_IIDR:
+		reg = vgic_mmio_read_v3_misc(vcpu, addr, len);
+		if ((reg ^ val) & ~GICD_IIDR_REVISION_MASK)
+			return -EINVAL;
+
+		reg = FIELD_GET(GICD_IIDR_REVISION_MASK, reg);
+		switch (reg) {
+		case KVM_VGIC_IMP_REV_2:
+		case KVM_VGIC_IMP_REV_3:
+			dist->implementation_rev = reg;
+			return 0;
+		default:
+			return -EINVAL;
+		}
 	case GICD_CTLR:
 		/* Not a GICv4.1? No HW SGIs */
 		if (!kvm_vgic_global_state.has_gicv4_1)
@@ -232,8 +246,13 @@ static unsigned long vgic_mmio_read_v3r_ctlr(struct kvm_vcpu *vcpu,
 					     gpa_t addr, unsigned int len)
 {
 	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+	unsigned long val;
+
+	val = atomic_read(&vgic_cpu->ctlr);
+	if (vcpu->kvm->arch.vgic.implementation_rev >= KVM_VGIC_IMP_REV_3)
+		val |= GICR_CTLR_IR | GICR_CTLR_CES;
 
-	return vgic_cpu->lpis_enabled ? GICR_CTLR_ENABLE_LPIS : 0;
+	return val;
 }
 
 static void vgic_mmio_write_v3r_ctlr(struct kvm_vcpu *vcpu,
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 401236f97cf2..2d8f2e90edc2 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -231,6 +231,9 @@ struct vgic_dist {
 
 	/* Implementation revision as reported in the GICD_IIDR */
 	u32			implementation_rev;
+#define KVM_VGIC_IMP_REV_2	2 /* GICv2 restorable groups */
+#define KVM_VGIC_IMP_REV_3	3 /* GICv3 GICR_CTLR.{IW,CES,RWP} */
+#define KVM_VGIC_IMP_REV_LATEST	KVM_VGIC_IMP_REV_3
 
 	/* Userspace can write to GICv2 IGROUPR */
 	bool			v2_groups_user_writable;
-- 
2.34.1