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Re: [PATCH v3 1/2] ppc/spapr: Introduce SPAPR_IRQ_NR_IPIS to refer IRQ r


From: Cédric Le Goater
Subject: Re: [PATCH v3 1/2] ppc/spapr: Introduce SPAPR_IRQ_NR_IPIS to refer IRQ range for CPU IPIs.
Date: Thu, 23 Nov 2023 09:50:24 +0100
User-agent: Mozilla Thunderbird

On 11/23/23 06:57, Harsh Prateek Bora wrote:
spapr_irq_init currently uses existing macro SPAPR_XIRQ_BASE to refer to
the range of CPU IPIs during initialization of nr-irqs property.
It is more appropriate to have its own define which can be further
reused as appropriate for correct interpretation.

Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Suggested-by: Cedric Le Goater <clg@kaod.org>

One comment below

Reviewed-by: Cédric Le Goater <clg@kaod.org>

---
  include/hw/ppc/spapr_irq.h | 14 +++++++++++++-
  hw/ppc/spapr_irq.c         |  6 ++++--
  2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/include/hw/ppc/spapr_irq.h b/include/hw/ppc/spapr_irq.h
index c22a72c9e2..4fd2d5853d 100644
--- a/include/hw/ppc/spapr_irq.h
+++ b/include/hw/ppc/spapr_irq.h
@@ -14,9 +14,21 @@
  #include "qom/object.h"
/*
- * IRQ range offsets per device type
+ * The XIVE IRQ backend uses the same layout as the XICS backend but
+ * covers the full range of the IRQ number space. The IRQ numbers for
+ * the CPU IPIs are allocated at the bottom of this space, below 4K,
+ * to preserve compatibility with XICS which does not use that range.
+ */
+
+/*
+ * CPU IPI range (XIVE only)
   */
  #define SPAPR_IRQ_IPI        0x0
+#define SPAPR_IRQ_NR_IPIS    0x1000
+
+/*
+ * IRQ range offsets per device type
+ */
#define SPAPR_XIRQ_BASE XICS_IRQ_BASE /* 0x1000 */
  #define SPAPR_IRQ_EPOW       (SPAPR_XIRQ_BASE + 0x0000)
diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
index a0d1e1298e..97b2fc42ab 100644
--- a/hw/ppc/spapr_irq.c
+++ b/hw/ppc/spapr_irq.c
@@ -23,6 +23,8 @@
#include "trace.h" +QEMU_BUILD_BUG_ON(SPAPR_IRQ_NR_IPIS > SPAPR_XIRQ_BASE);
+

I would have put the check in include/hw/ppc/spapr_irq.h but since
SPAPR_XIRQ_BASE is only used in hw/ppc/spapr_irq.c which is always
compiled, this is fine. You might want to change that in case a
respin is asked for.

Thanks,

C.


  static const TypeInfo spapr_intc_info = {
      .name = TYPE_SPAPR_INTC,
      .parent = TYPE_INTERFACE,
@@ -329,7 +331,7 @@ void spapr_irq_init(SpaprMachineState *spapr, Error **errp)
          int i;
dev = qdev_new(TYPE_SPAPR_XIVE);
-        qdev_prop_set_uint32(dev, "nr-irqs", smc->nr_xirqs + SPAPR_XIRQ_BASE);
+        qdev_prop_set_uint32(dev, "nr-irqs", smc->nr_xirqs + 
SPAPR_IRQ_NR_IPIS);
          /*
           * 8 XIVE END structures per CPU. One for each available
           * priority
@@ -356,7 +358,7 @@ void spapr_irq_init(SpaprMachineState *spapr, Error **errp)
      }
spapr->qirqs = qemu_allocate_irqs(spapr_set_irq, spapr,
-                                      smc->nr_xirqs + SPAPR_XIRQ_BASE);
+                                      smc->nr_xirqs + SPAPR_IRQ_NR_IPIS);
/*
       * Mostly we don't actually need this until reset, except that not




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