[Qemu-devel] [PATCH v2 1/8] xics: Add flags for interrupts

[Alexey Kardashevskiy <aik@ozlabs.ru>]

The existing interrupt allocation scheme in SPAPR assumes that
interrupts are allocated at the start time, continously and the config
will not change. However, there are cases when this is not going to work
such as:

1. migration - we will have to have an ability to choose interrupt
numbers for devices in the command line and this will create gaps in
interrupt space.

2. PCI hotplug - interrupts from unplugged device need to be returned
back to interrupt pool, otherwise we will quickly run out of interrupts.

This replaces a separate lslsi[] array with a byte in the ICSIRQState
struct and defines "LSI" and "MSI" flags. Neither of these flags set
signals that the descriptor is not allocated and not in use.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 hw/intc/xics.c        | 23 ++++++++++++++++-------
 hw/intc/xics_kvm.c    |  5 ++---
 include/hw/ppc/xics.h |  6 +++++-
 3 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/hw/intc/xics.c b/hw/intc/xics.c
index 64aabe7..220ca0e 100644
--- a/hw/intc/xics.c
+++ b/hw/intc/xics.c
@@ -438,7 +438,7 @@ static void ics_set_irq(void *opaque, int srcno, int val)
 {
     ICSState *ics = (ICSState *)opaque;
 
-    if (ics->islsi[srcno]) {
+    if (ics->irqs[srcno].flags & XICS_FLAGS_IRQ_LSI) {
         set_irq_lsi(ics, srcno, val);
     } else {
         set_irq_msi(ics, srcno, val);
@@ -475,7 +475,7 @@ static void ics_write_xive(ICSState *ics, int nr, int server,
 
     trace_xics_ics_write_xive(nr, srcno, server, priority);
 
-    if (ics->islsi[srcno]) {
+    if (ics->irqs[srcno].flags & XICS_FLAGS_IRQ_LSI) {
         write_xive_lsi(ics, srcno);
     } else {
         write_xive_msi(ics, srcno);
@@ -497,7 +497,7 @@ static void ics_resend(ICSState *ics)
 
     for (i = 0; i < ics->nr_irqs; i++) {
         /* FIXME: filter by server#? */
-        if (ics->islsi[i]) {
+        if (ics->irqs[i].flags & XICS_FLAGS_IRQ_LSI) {
             resend_lsi(ics, i);
         } else {
             resend_msi(ics, i);
@@ -512,7 +512,7 @@ static void ics_eoi(ICSState *ics, int nr)
 
     trace_xics_ics_eoi(nr);
 
-    if (ics->islsi[srcno]) {
+    if (ics->irqs[srcno].flags & XICS_FLAGS_IRQ_LSI) {
         irq->status &= ~XICS_STATUS_SENT;
     }
 }
@@ -609,7 +609,6 @@ static void ics_realize(DeviceState *dev, Error **errp)
         return;
     }
     ics->irqs = g_malloc0(ics->nr_irqs * sizeof(ICSIRQState));
-    ics->islsi = g_malloc0(ics->nr_irqs * sizeof(bool));
     ics->qirqs = qemu_allocate_irqs(ics_set_irq, ics, ics->nr_irqs);
 }
 
@@ -646,11 +645,21 @@ qemu_irq xics_get_qirq(XICSState *icp, int irq)
     return icp->ics->qirqs[irq - icp->ics->offset];
 }
 
+static void ics_set_irq_type(ICSState *ics, int srcno, bool lsi)
+{
+    assert(!(ics->irqs[srcno].flags & XICS_FLAGS_IRQ_MASK));
+
+    ics->irqs[srcno].flags |=
+        lsi ? XICS_FLAGS_IRQ_LSI : XICS_FLAGS_IRQ_MSI;
+}
+
 void xics_set_irq_type(XICSState *icp, int irq, bool lsi)
 {
-    assert(ics_valid_irq(icp->ics, irq));
+    ICSState *ics = icp->ics;
 
-    icp->ics->islsi[irq - icp->ics->offset] = lsi;
+    assert(ics_valid_irq(ics, irq));
+
+    ics_set_irq_type(ics, irq - ics->offset, lsi);
 }
 
 /*
diff --git a/hw/intc/xics_kvm.c b/hw/intc/xics_kvm.c
index 09476ae..8719a88 100644
--- a/hw/intc/xics_kvm.c
+++ b/hw/intc/xics_kvm.c
@@ -224,7 +224,7 @@ static int ics_set_kvm_state(ICSState *ics, int version_id)
             state |= KVM_XICS_MASKED;
         }
 
-        if (ics->islsi[i]) {
+        if (ics->irqs[i].flags & XICS_FLAGS_IRQ_LSI) {
             state |= KVM_XICS_LEVEL_SENSITIVE;
             if (irq->status & XICS_STATUS_ASSERTED) {
                 state |= KVM_XICS_PENDING;
@@ -253,7 +253,7 @@ static void ics_kvm_set_irq(void *opaque, int srcno, int val)
     int rc;
 
     args.irq = srcno + ics->offset;
-    if (!ics->islsi[srcno]) {
+    if (ics->irqs[srcno].flags & XICS_FLAGS_IRQ_MSI) {
         if (!val) {
             return;
         }
@@ -290,7 +290,6 @@ static void ics_kvm_realize(DeviceState *dev, Error **errp)
         return;
     }
     ics->irqs = g_malloc0(ics->nr_irqs * sizeof(ICSIRQState));
-    ics->islsi = g_malloc0(ics->nr_irqs * sizeof(bool));
     ics->qirqs = qemu_allocate_irqs(ics_kvm_set_irq, ics, ics->nr_irqs);
 }
 
diff --git a/include/hw/ppc/xics.h b/include/hw/ppc/xics.h
index 0d7673d..fa8e9c2 100644
--- a/include/hw/ppc/xics.h
+++ b/include/hw/ppc/xics.h
@@ -136,7 +136,6 @@ struct ICSState {
     uint32_t nr_irqs;
     uint32_t offset;
     qemu_irq *qirqs;
-    bool *islsi;
     ICSIRQState *irqs;
     XICSState *icp;
 };
@@ -150,6 +149,11 @@ struct ICSIRQState {
 #define XICS_STATUS_REJECTED           0x4
 #define XICS_STATUS_MASKED_PENDING     0x8
     uint8_t status;
+/* (flags & XICS_FLAGS_IRQ_MASK) == 0 means the interrupt is not allocated */
+#define XICS_FLAGS_IRQ_LSI             0x1
+#define XICS_FLAGS_IRQ_MSI             0x2
+#define XICS_FLAGS_IRQ_MASK            0x3
+    uint8_t flags;
 };
 
 qemu_irq xics_get_qirq(XICSState *icp, int irq);
-- 
1.9.rc0