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Re: [qemu-s390x] [PATCH v2 2/6] s390x/vfio: ap: Use the APdevice as a ch

From: Pierre Morel
Subject: Re: [qemu-s390x] [PATCH v2 2/6] s390x/vfio: ap: Use the APdevice as a child of the APBus
Date: Fri, 30 Nov 2018 10:31:00 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1

On 29/11/2018 21:42, Tony Krowiak wrote:
On 11/22/18 11:35 AM, Pierre Morel wrote:
Two good reasons to use the base device as a child of the
- We can easily find the device without traversing the qtree.
- In case we have different APdevice instantiation, VFIO with
   interception or emulation, we will need the APDevice as
   a parent device.

Signed-off-by: Pierre Morel <address@hidden>
  hw/s390x/ap-device.c         | 22 ++++++++++++++++++++++
  hw/vfio/ap.c                 | 16 ++++++----------
  include/hw/s390x/ap-device.h |  2 ++
  3 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/hw/s390x/ap-device.c b/hw/s390x/ap-device.c
index f5ac8db..554d5aa 100644
--- a/hw/s390x/ap-device.c
+++ b/hw/s390x/ap-device.c
@@ -11,13 +11,35 @@
  #include "qemu/module.h"
  #include "qapi/error.h"
  #include "hw/qdev.h"
+#include "hw/s390x/ap-bridge.h"
  #include "hw/s390x/ap-device.h"
+APDevice *s390_get_ap(void)

How about ap_get_device(void)?

Yes, keep same conventions.

+    static DeviceState *apb;

Why static if you call s390_get_ap_bridge()
to retrieve it without first checking for NULL?

static are initialized as NULL.

+    BusState *bus;
+    BusChild *child;
+    static APDevice *ap;
+    if (ap) {
+        return ap;
+    }
+    apb = s390_get_ap_bridge();
+    /* We have only a single child on the BUS */
+    bus = qdev_get_child_bus(apb, TYPE_AP_BUS
+    child = QTAILQ_FIRST(&bus->children);
+    assert(child != NULL);
+    ap = DO_UPCAST(APDevice, parent_obj, child->child);

I received a comment from Thomas Huth in Message ID
that DO_UPCAST should be avoided in new code. You should
create an AP_DEVICE macro for this in ap-device.h

Thanks I will do.


Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany

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