[Qemu-devel] [PATCH v4 2/9] ppc/xics: Fix migration failure with kernel-irqchip=off

[Nikunj A Dadhania]

With a single cpu VM running with kernel-irqchip=off and a flood ping
running in the guest. Migration fails once in few times.

Found that whenever there is an interrupt (in this case lsi int 3 from
e1000), we raise an interrupt using qemu_irq_pulse() and also see that
the kvm ioctl is complete.

67351@1468011062.810020:xics_set_irq_lsi set_irq_lsi: srcno 3 [irq 0x1003]
67351@1468011062.810031:xics_icp_irq cpu 0 trying to deliver irq 0x1003 
priority 0x5
67351@1468011062.810038:xics_icp_raise raising IRQ new XIRR=0xff001003
new pending priority=0x5

After migration on the target side, interrupts(prio 0x5) are rejected as
there is a interrupt pending (pending_priority 0x5). Moreover, we never
get an icp_accept from the guest, so it hangs and crashes.

Basically, resend the irq pulse(lsi) to the guest.

Signed-off-by: Nikunj A Dadhania <nik...@linux.vnet.ibm.com>
---
 hw/intc/xics.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/hw/intc/xics.c b/hw/intc/xics.c
index 69162f0..f765b08 100644
--- a/hw/intc/xics.c
+++ b/hw/intc/xics.c
@@ -209,7 +209,7 @@ static const TypeInfo xics_common_info = {
 #define CPPR(ss)   (((ss)->xirr) >> 24)
 
 static void ics_reject(ICSState *ics, int nr);
-static void ics_resend(ICSState *ics);
+static void ics_resend(ICSState *ics, int server);
 static void ics_eoi(ICSState *ics, int nr);
 
 static void icp_check_ipi(XICSState *xics, int server)
@@ -238,7 +238,7 @@ static void icp_resend(XICSState *xics, int server)
     if (ss->mfrr < CPPR(ss)) {
         icp_check_ipi(xics, server);
     }
-    ics_resend(xics->ics);
+    ics_resend(xics->ics, server);
 }
 
 void icp_set_cppr(XICSState *xics, int server, uint8_t cppr)
@@ -512,13 +512,24 @@ static void ics_reject(ICSState *ics, int nr)
     }
 }
 
-static void ics_resend(ICSState *ics)
+static void ics_resend(ICSState *ics, int server)
 {
     int i;
+    ICPState *ss = ics->xics->ss + server;
+    ICSIRQState *irq;
 
     for (i = 0; i < ics->nr_irqs; i++) {
         /* FIXME: filter by server#? */
-        if (ics->irqs[i].flags & XICS_FLAGS_IRQ_LSI) {
+        irq = &ics->irqs[i];
+        if (!(irq->flags & XICS_FLAGS_IRQ_MASK)) {
+            continue;
+        }
+
+        if (irq->flags & XICS_FLAGS_IRQ_LSI) {
+            if (irq->status & XICS_STATUS_SENT) {
+                qemu_irq_raise(ss->output);
+                continue;
+            }
             resend_lsi(ics, i);
         } else {
             resend_msi(ics, i);
-- 
2.7.4