KVM: arm64: vgic-v3: Align emulated cpuif LPI state machine with the pseudocode

Having realised that a virtual LPI does transition through an active
state that does not exist on bare metal, align the CPU interface
emulation with the behaviour specified in the architecture pseudocode.

The LPIs now transition to active on IAR read, and to inactive on
EOI write. Special care is taken not to increment the EOIcount for
an LPI that isn't present in the LRs.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211010150910.2911495-6-maz@kernel.org

arch/arm64/kvm/hyp/vgic-v3-sr.c

@@ -695,9 +695,7 @@ static void __vgic_v3_read_iar(struct kvm_vcpu *vcpu, u32 vmcr, int rt)
 		goto spurious;
 
 	lr_val &= ~ICH_LR_STATE;
-	/* No active state for LPIs */
-	if ((lr_val & ICH_LR_VIRTUAL_ID_MASK) <= VGIC_MAX_SPI)
-		lr_val |= ICH_LR_ACTIVE_BIT;
+	lr_val |= ICH_LR_ACTIVE_BIT;
 	__gic_v3_set_lr(lr_val, lr);
 	__vgic_v3_set_active_priority(lr_prio, vmcr, grp);
 	vcpu_set_reg(vcpu, rt, lr_val & ICH_LR_VIRTUAL_ID_MASK);
@@ -764,20 +762,18 @@ static void __vgic_v3_write_eoir(struct kvm_vcpu *vcpu, u32 vmcr, int rt)
 	/* Drop priority in any case */
 	act_prio = __vgic_v3_clear_highest_active_priority();
 
-	/* If EOIing an LPI, no deactivate to be performed */
-	if (vid >= VGIC_MIN_LPI)
-		return;
-
-	/* EOImode == 1, nothing to be done here */
-	if (vmcr & ICH_VMCR_EOIM_MASK)
-		return;
-
 	lr = __vgic_v3_find_active_lr(vcpu, vid, &lr_val);
 	if (lr == -1) {
-		__vgic_v3_bump_eoicount();
+		/* Do not bump EOIcount for LPIs that aren't in the LRs */
+		if (!(vid >= VGIC_MIN_LPI))
+			__vgic_v3_bump_eoicount();
 		return;
 	}
 
+	/* EOImode == 1 and not an LPI, nothing to be done here */
+	if ((vmcr & ICH_VMCR_EOIM_MASK) && !(vid >= VGIC_MIN_LPI))
+		return;
+
 	lr_prio = (lr_val & ICH_LR_PRIORITY_MASK) >> ICH_LR_PRIORITY_SHIFT;
 
 	/* If priorities or group do not match, the guest has fscked-up. */