[Qemu-devel] [RFC PATCH v2 13/21] ppc/xive: handle interrupt acknowledgment by the O/S

["Cédric Le Goater" <clg@kaod.org>]

When an O/S Exception is raised, the O/S acknowledges the interrupt
with a special read in the TIMA. If the EO bit of the Notification
Source Register (NSR) is set (and it should), the Current Processor
Priority Register (CPPR) takes the value of the Pending Interrupt
Priority Register (PIPR), which contains the priority of the most
favored pending notification. The bit number corresponding to the
priority of the pending interrupt is reseted in the Interrupt Pending
Buffer (IPB) and so is the EO bit of the NSR.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
---
 hw/intc/spapr_xive.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
index e5d4b723b7e0..ad3ff91b13ea 100644
--- a/hw/intc/spapr_xive.c
+++ b/hw/intc/spapr_xive.c
@@ -50,7 +50,24 @@ static uint8_t ipb_to_pipr(uint8_t ibp)
 
 static uint64_t spapr_xive_icp_accept(ICPState *icp)
 {
-    return 0;
+    uint8_t nsr = icp->tima_os[TM_NSR];
+
+    qemu_irq_lower(icp->output);
+
+    if (icp->tima_os[TM_NSR] & TM_QW1_NSR_EO) {
+        uint8_t cppr = icp->tima_os[TM_PIPR];
+
+        icp->tima_os[TM_CPPR] = cppr;
+
+        /* Reset the pending buffer bit */
+        icp->tima_os[TM_IPB] &= ~priority_to_ipb(cppr);
+        icp->tima_os[TM_PIPR] = ipb_to_pipr(icp->tima_os[TM_IPB]);
+
+        /* Drop Exception bit for OS */
+        icp->tima_os[TM_NSR] &= ~TM_QW1_NSR_EO;
+    }
+
+    return (nsr << 8) | icp->tima_os[TM_CPPR];
 }
 
 static void spapr_xive_icp_notify(ICPState *icp)
-- 
2.13.5