Re: [Qemu-devel] [PATCH 1/1] s390x: create a compat s390 phb for <=2.10

[Yi Min Zhao]

在 2017/9/27 下午5:47, Cornelia Huck 写道:

On Tue, 26 Sep 2017 20:40:25 +0200
David Hildenbrand <da...@redhat.com> wrote:

On 26.09.2017 18:20, Cornelia Huck wrote:

d32bd032d8 ("s390x/ccw: create s390 phb conditionally") made
creating the s390 phb dependant on the zpci facility. This broke
migration from pre-cpu model machines which was fixed with
8ad9087c4a ("s390x/ccw: create s390 phb for compat reasons as well").
However, that is not enough: Migration from 2.10 with -cpu z13
breaks as well.

Let's create a phb for all pre-2.11 compat machines to fix this.
We leave the zpci facility off to avoid a guest-visible change
with cpu models on.

Reported-by: Christian Borntraeger <borntrae...@de.ibm.com>
Fixes: d32bd032d8 ("s390x/ccw: create s390 phb conditionally")
Signed-off-by: Cornelia Huck <coh...@redhat.com>
---
  hw/s390x/s390-virtio-ccw.c         | 8 +++++++-
  include/hw/s390x/s390-virtio-ccw.h | 1 +
  2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 1bcb7000ab..981f1c4336 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -247,6 +247,8 @@ static void s390_create_virtio_net(BusState *bus, const 
char *name)
      }
  }

+static S390CcwMachineClass *get_machine_class(void);

+
  static void ccw_init(MachineState *machine)
  {
      int ret;
@@ -266,7 +268,7 @@ static void ccw_init(MachineState *machine)
                        machine->initrd_filename, "s390-ccw.img",
                        "s390-netboot.img", true);

- if (s390_has_feat(S390_FEAT_ZPCI)) {

+    if (s390_has_feat(S390_FEAT_ZPCI) || get_machine_class()->phb_compat) {
          DeviceState *dev = qdev_create(NULL, TYPE_S390_PCI_HOST_BRIDGE);
          object_property_add_child(qdev_get_machine(),
                                    TYPE_S390_PCI_HOST_BRIDGE,
@@ -407,6 +409,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void 
*data)
      s390mc->cpu_model_allowed = true;
      s390mc->css_migration_enabled = true;
      s390mc->gs_allowed = true;
+    s390mc->phb_compat = false;
      mc->init = ccw_init;
      mc->reset = s390_machine_reset;
      mc->hot_add_cpu = s390_hot_add_cpu;
@@ -716,6 +719,9 @@ static void ccw_machine_2_10_instance_options(MachineState 
*machine)

static void ccw_machine_2_10_class_options(MachineClass *mc)

  {
+    S390CcwMachineClass *s390mc = S390_MACHINE_CLASS(mc);
+
+    s390mc->phb_compat = pci_available;
      ccw_machine_2_11_class_options(mc);
      SET_MACHINE_COMPAT(mc, CCW_COMPAT_2_10);
  }
diff --git a/include/hw/s390x/s390-virtio-ccw.h 
b/include/hw/s390x/s390-virtio-ccw.h
index a9a90c2022..fb717afe92 100644
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -41,6 +41,7 @@ typedef struct S390CcwMachineClass {
      bool cpu_model_allowed;
      bool css_migration_enabled;
      bool gs_allowed;
+    bool phb_compat;
  } S390CcwMachineClass;

/* runtime-instrumentation allowed by the machine */

I'd really really really (did I mention really?) favor something like a
dummy device, because we could easily handle the !CONFIG_PCI case then.

All these compat options and conditions will kill us someday... we're
already patching around that whole stuff way too much.

If we ever unconditionally created a device, we should keep doing so.

Yes, that whole thing is horrible, especially interaction with compat
machines.

Do you have an idea on how to create such a dummy device (without
having to effectively copy a lot of configured-out code)?

How about in s390_pcihost_hot_plug() we check s390_has_feat(zpci)?
If no zpci feature, we avoid plugging any pci device.
Then we could always create phb.
I think pcibus's vmstate is only data to migrate.