x86: ioapic: add support for explicit EOI

Some old Linux kernels (upstream before v4.0), or any released RHEL
kernels has problem in sending APIC EOI when IR is enabled. Meanwhile,
many of them only support explicit EOI for IOAPIC, which is only
introduced in IOAPIC version 0x20. This patch provide a way to boost
QEMU IOAPIC to version 0x20, in order for QEMU to correctly receive EOI
messages.

Without boosting IOAPIC version to 0x20, kernels before commit d32932d
("x86/irq: Convert IOAPIC to use hierarchical irqdomain interfaces")
will have trouble enabling both IR and level-triggered interrupt devices
(like e1000).

To upgrade IOAPIC to version 0x20, we need to specify:

  -global ioapic.version=0x20

To be compatible with old systems, 0x11 will still be the default IOAPIC
version. Here 0x11 and 0x20 are the only versions to be supported.

One thing to mention: this patch only applies to emulated IOAPIC. It
does not affect kernel IOAPIC behavior.

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <1470059959-372-1-git-send-email-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 21 insertions, 1 deletions

diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c
index a00d88210a..31791b0986 100644
--- a/hw/intc/ioapic.c
+++ b/hw/intc/ioapic.c
@@ -21,6 +21,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
 #include "monitor/monitor.h"
 #include "hw/hw.h"
 #include "hw/i386/pc.h"
@@ -269,7 +270,7 @@ ioapic_mem_read(void *opaque, hwaddr addr, unsigned int size)
             val = s->id << IOAPIC_ID_SHIFT;
             break;
         case IOAPIC_REG_VER:
-            val = IOAPIC_VERSION |
+            val = s->version |
                 ((IOAPIC_NUM_PINS - 1) << IOAPIC_VER_ENTRIES_SHIFT);
             break;
         default:
@@ -358,6 +359,13 @@ ioapic_mem_write(void *opaque, hwaddr addr, uint64_t val,
             }
         }
         break;
+    case IOAPIC_EOI:
+        /* Explicit EOI is only supported for IOAPIC version 0x20 */
+        if (size != 4 || s->version != 0x20) {
+            break;
+        }
+        ioapic_eoi_broadcast(val);
+        break;
     }
 
     ioapic_update_kvm_routes(s);
@@ -391,6 +399,12 @@ static void ioapic_realize(DeviceState *dev, Error **errp)
 {
     IOAPICCommonState *s = IOAPIC_COMMON(dev);
 
+    if (s->version != 0x11 && s->version != 0x20) {
+        error_report("IOAPIC only supports version 0x11 or 0x20 "
+                     "(default: 0x11).");
+        exit(1);
+    }
+
     memory_region_init_io(&s->io_memory, OBJECT(s), &ioapic_io_ops, s,
                           "ioapic", 0x1000);
 
@@ -401,6 +415,11 @@ static void ioapic_realize(DeviceState *dev, Error **errp)
     qemu_add_machine_init_done_notifier(&s->machine_done);
 }
 
+static Property ioapic_properties[] = {
+    DEFINE_PROP_UINT8("version", IOAPICCommonState, version, 0x11),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
 static void ioapic_class_init(ObjectClass *klass, void *data)
 {
     IOAPICCommonClass *k = IOAPIC_COMMON_CLASS(klass);
@@ -408,6 +427,7 @@ static void ioapic_class_init(ObjectClass *klass, void *data)
 
     k->realize = ioapic_realize;
     dc->reset = ioapic_reset_common;
+    dc->props = ioapic_properties;
 }
 
 static const TypeInfo ioapic_info = {