[Qemu-devel] [PATCH 4/8] spapr: split the IRQ number space for LSI interrupts

[Cédric Le Goater]

The nature of an interrupt, MSI or LSI, is stored under the flag
attribute of the ICSIRQState array. To reduce the use of this array
and consequently of the ICSState object (needed to introduce for the
new XIVE model), we choose to split the IRQ number space of the
machine in two: first the LSIs and then the MSIs.

This also has the benefit to keep the LSI IRQ numbers in a well known
range which will be useful for PHB hotplug.

For compatibility with older machines, we use the machine class flag
'pre_2_11_has_no_bitmap'.

Signed-off-by: Cédric Le Goater <address@hidden>
---
 hw/intc/xics_spapr.c  |  6 +++---
 hw/ppc/spapr.c        | 25 ++++++++++++++++++++++---
 include/hw/ppc/xics.h |  2 +-
 3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/hw/intc/xics_spapr.c b/hw/intc/xics_spapr.c
index f2e20bca5b2e..e1f158302a6a 100644
--- a/hw/intc/xics_spapr.c
+++ b/hw/intc/xics_spapr.c
@@ -257,7 +257,7 @@ int spapr_ics_alloc(ICSState *ics, int irq_hint, bool lsi, 
Error **errp)
         }
         irq = irq_hint;
     } else {
-        irq = xic->irq_alloc_block(ics->xics, 1, 0);
+        irq = xic->irq_alloc_block(ics->xics, 1, 0, lsi);
         if (irq < 0) {
             error_setg(errp, "can't allocate IRQ: no IRQ left");
             return -1;
@@ -291,9 +291,9 @@ int spapr_ics_alloc_block(ICSState *ics, int num, bool lsi,
     if (align) {
         assert((num == 1) || (num == 2) || (num == 4) ||
                (num == 8) || (num == 16) || (num == 32));
-        first = xic->irq_alloc_block(ics->xics, num, num);
+        first = xic->irq_alloc_block(ics->xics, num, num, lsi);
     } else {
-        first = xic->irq_alloc_block(ics->xics, num, 0);
+        first = xic->irq_alloc_block(ics->xics, num, 0, lsi);
     }
     if (first < 0) {
         error_setg(errp, "can't find a free %d-IRQ block", num);
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index b33eebe44906..5e42e3329ef4 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1696,6 +1696,13 @@ static const VMStateDescription vmstate_spapr_patb_entry 
= {
     },
 };
 
+/*
+ * Let's provision 4 LSIs per PHBs
+ */
+#define SPAPR_MAX_PHBS ((SPAPR_PCI_LIMIT - SPAPR_PCI_BASE) / \
+                        SPAPR_PCI_MEM64_WIN_SIZE - 1)
+#define SPAPR_MAX_LSI (SPAPR_MAX_PHBS * 4)
+
 static bool spapr_irq_map_needed(void *opaque)
 {
     sPAPRMachineState *spapr = opaque;
@@ -3523,8 +3530,6 @@ static void spapr_phb_placement(sPAPRMachineState *spapr, 
uint32_t index,
      * 1TiB 64-bit MMIO windows for each PHB.
      */
     const uint64_t base_buid = 0x800000020000000ULL;
-#define SPAPR_MAX_PHBS ((SPAPR_PCI_LIMIT - SPAPR_PCI_BASE) / \
-                        SPAPR_PCI_MEM64_WIN_SIZE - 1)
     int i;
 
     /* Sanity check natural alignments */
@@ -3583,18 +3588,32 @@ static bool spapr_irq_test(XICSFabric *xi, int irq)
     return test_bit(srcno, spapr->irq_map);
 }
 
-static int spapr_irq_alloc_block(XICSFabric *xi, int count, int align)
+/*
+ * Split the IRQ number space of the machine in two: first the LSIs
+ * and then the MSIs. This allows us to keep the LSI IRQ numbers in a
+ * well known range which is useful for PHB hotplug.
+ */
+static int spapr_irq_alloc_block(XICSFabric *xi, int count, int align, bool 
lsi)
 {
     sPAPRMachineState *spapr = SPAPR_MACHINE(xi);
+    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
     int start = 0;
     int srcno;
 
+    if (!lsi && !smc->pre_2_11_has_no_bitmap) {
+        start = SPAPR_MAX_LSI;
+    }
+
     srcno = bitmap_find_next_zero_area(spapr->irq_map, spapr->nr_irqs, start,
                                        count, align);
     if (srcno == spapr->nr_irqs) {
         return -1;
     }
 
+    if (lsi && !smc->pre_2_11_has_no_bitmap && srcno >= SPAPR_MAX_LSI) {
+        return -1;
+    }
+
     bitmap_set(spapr->irq_map, srcno, count);
     return srcno + spapr->irq_base;
 }
diff --git a/include/hw/ppc/xics.h b/include/hw/ppc/xics.h
index 30e7f2e0a7dd..c8e6637d16e4 100644
--- a/include/hw/ppc/xics.h
+++ b/include/hw/ppc/xics.h
@@ -177,7 +177,7 @@ typedef struct XICSFabricClass {
     ICPState *(*icp_get)(XICSFabric *xi, int server);
     /* IRQ allocator helpers */
     bool (*irq_test)(XICSFabric *xi, int irq);
-    int (*irq_alloc_block)(XICSFabric *xi, int count, int align);
+    int (*irq_alloc_block)(XICSFabric *xi, int count, int align, bool lsi);
     void (*irq_free_block)(XICSFabric *xi, int irq, int num);
 } XICSFabricClass;
 
-- 
2.13.6