KVM: PPC: Book 3S: XICS: Implement ICS P/Q states

This patch implements P(Presented)/Q(Queued) states for ICS irqs.

When the interrupt is presented, set P. Present if P was not set.
If P is already set, don't present again, set Q.
When the interrupt is EOI'ed, move Q into P (and clear Q). If it is
set, re-present.

The asserted flag used by LSI is also incorporated into the P bit.

When the irq state is saved, P/Q bits are also saved, they need some
qemu modifications to be recognized and passed around to be restored.
KVM_XICS_PENDING bit set and saved should also indicate
KVM_XICS_PRESENTED bit set and saved. But it is possible some old
code doesn't have/recognize the P bit, so when we restore, we set P
for PENDING bit, too.

The idea and much of the code come from Ben.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

1 files changed, 70 insertions, 30 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_rm_xics.c b/arch/powerpc/kvm/book3s_hv_rm_xics.c
index 16349c9e86ba..30f82c79de5d 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_xics.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_xics.c
@@ -672,51 +672,39 @@ int kvmppc_rm_h_cppr(struct kvm_vcpu *vcpu, unsigned long cppr)
 	return check_too_hard(xics, icp);
 }
 
-int kvmppc_rm_h_eoi(struct kvm_vcpu *vcpu, unsigned long xirr)
+static int ics_rm_eoi(struct kvm_vcpu *vcpu, u32 irq)
 {
 	struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
 	struct kvmppc_icp *icp = vcpu->arch.icp;
 	struct kvmppc_ics *ics;
 	struct ics_irq_state *state;
-	u32 irq = xirr & 0x00ffffff;
 	u16 src;
-
-	if (!xics || !xics->real_mode)
-		return H_TOO_HARD;
+	u32 pq_old, pq_new;
 
 	/*
-	 * ICP State: EOI
-	 *
-	 * Note: If EOI is incorrectly used by SW to lower the CPPR
-	 * value (ie more favored), we do not check for rejection of
-	 * a pending interrupt, this is a SW error and PAPR sepcifies
-	 * that we don't have to deal with it.
+	 * ICS EOI handling: For LSI, if P bit is still set, we need to
+	 * resend it.
 	 *
-	 * The sending of an EOI to the ICS is handled after the
-	 * CPPR update
-	 *
-	 * ICP State: Down_CPPR which we handle
-	 * in a separate function as it's shared with H_CPPR.
+	 * For MSI, we move Q bit into P (and clear Q). If it is set,
+	 * resend it.
 	 */
-	icp_rm_down_cppr(xics, icp, xirr >> 24);
 
-	/* IPIs have no EOI */
-	if (irq == XICS_IPI)
-		goto bail;
-	/*
-	 * EOI handling: If the interrupt is still asserted, we need to
-	 * resend it. We can take a lockless "peek" at the ICS state here.
-	 *
-	 * "Message" interrupts will never have "asserted" set
-	 */
 	ics = kvmppc_xics_find_ics(xics, irq, &src);
 	if (!ics)
 		goto bail;
+
 	state = &ics->irq_state[src];
 
-	/* Still asserted, resend it */
-	if (state->asserted)
-		icp_rm_deliver_irq(xics, icp, irq);
+	if (state->lsi)
+		pq_new = state->pq_state;
+	else
+		do {
+			pq_old = state->pq_state;
+			pq_new = pq_old >> 1;
+		} while (cmpxchg(&state->pq_state, pq_old, pq_new) != pq_old);
+
+	if (pq_new & PQ_PRESENTED)
+		icp_rm_deliver_irq(xics, NULL, irq);
 
 	if (!hlist_empty(&vcpu->kvm->irq_ack_notifier_list)) {
 		icp->rm_action |= XICS_RM_NOTIFY_EOI;
@@ -737,10 +725,43 @@ int kvmppc_rm_h_eoi(struct kvm_vcpu *vcpu, unsigned long xirr)
 			state->intr_cpu = -1;
 		}
 	}
+
  bail:
 	return check_too_hard(xics, icp);
 }
 
+int kvmppc_rm_h_eoi(struct kvm_vcpu *vcpu, unsigned long xirr)
+{
+	struct kvmppc_xics *xics = vcpu->kvm->arch.xics;
+	struct kvmppc_icp *icp = vcpu->arch.icp;
+	u32 irq = xirr & 0x00ffffff;
+
+	if (!xics || !xics->real_mode)
+		return H_TOO_HARD;
+
+	/*
+	 * ICP State: EOI
+	 *
+	 * Note: If EOI is incorrectly used by SW to lower the CPPR
+	 * value (ie more favored), we do not check for rejection of
+	 * a pending interrupt, this is a SW error and PAPR specifies
+	 * that we don't have to deal with it.
+	 *
+	 * The sending of an EOI to the ICS is handled after the
+	 * CPPR update
+	 *
+	 * ICP State: Down_CPPR which we handle
+	 * in a separate function as it's shared with H_CPPR.
+	 */
+	icp_rm_down_cppr(xics, icp, xirr >> 24);
+
+	/* IPIs have no EOI */
+	if (irq == XICS_IPI)
+		return check_too_hard(xics, icp);
+
+	return ics_rm_eoi(vcpu, irq);
+}
+
 unsigned long eoi_rc;
 
 static void icp_eoi(struct irq_chip *c, u32 hwirq, __be32 xirr, bool *again)
@@ -827,14 +848,33 @@ long kvmppc_deliver_irq_passthru(struct kvm_vcpu *vcpu,
 {
 	struct kvmppc_xics *xics;
 	struct kvmppc_icp *icp;
+	struct kvmppc_ics *ics;
+	struct ics_irq_state *state;
 	u32 irq;
+	u16 src;
+	u32 pq_old, pq_new;
 
 	irq = irq_map->v_hwirq;
 	xics = vcpu->kvm->arch.xics;
 	icp = vcpu->arch.icp;
 
 	kvmppc_rm_handle_irq_desc(irq_map->desc);
-	icp_rm_deliver_irq(xics, icp, irq);
+
+	ics = kvmppc_xics_find_ics(xics, irq, &src);
+	if (!ics)
+		return 2;
+
+	state = &ics->irq_state[src];
+
+	/* only MSIs register bypass producers, so it must be MSI here */
+	do {
+		pq_old = state->pq_state;
+		pq_new = ((pq_old << 1) & 3) | PQ_PRESENTED;
+	} while (cmpxchg(&state->pq_state, pq_old, pq_new) != pq_old);
+
+	/* Test P=1, Q=0, this is the only case where we present */
+	if (pq_new == PQ_PRESENTED)
+		icp_rm_deliver_irq(xics, icp, irq);
 
 	/* EOI the interrupt */
 	icp_eoi(irq_desc_get_chip(irq_map->desc), irq_map->r_hwirq, xirr,