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Re: [Qemu-devel] [PATCH 5/8] [PATCH RFC v3] s390-qemu: cpu hotplug - ipi

From: Jason J. Herne
Subject: Re: [Qemu-devel] [PATCH 5/8] [PATCH RFC v3] s390-qemu: cpu hotplug - ipi_states enhancements
Date: Fri, 13 Sep 2013 11:17:56 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7

On 09/05/2013 08:01 AM, Andreas Färber wrote:
Am 01.08.2013 16:12, schrieb Jason J. Herne:
From: "Jason J. Herne" <address@hidden>

Modify s390_cpu_addr2state to allow fetching state information for cpu addresses
above smp_cpus.  Hotplug requires this capability.

Also add s390_cpu_set_state function to allow modification of ipi_state entries
during hotplug.

Signed-off-by: Jason J. Herne <address@hidden>
  hw/s390x/s390-virtio.c |    9 +++++----
  target-s390x/cpu.h     |    2 +-
  2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/hw/s390x/s390-virtio.c b/hw/s390x/s390-virtio.c
index 21e9124..5ad9cf3 100644
--- a/hw/s390x/s390-virtio.c
+++ b/hw/s390x/s390-virtio.c
@@ -54,12 +54,13 @@
  static VirtIOS390Bus *s390_bus;
  static S390CPU **ipi_states;

-S390CPU *s390_cpu_addr2state(uint16_t cpu_addr)
+void s390_cpu_set_ipistate(uint16_t cpu_addr, S390CPU *state)
-    if (cpu_addr >= smp_cpus) {
-        return NULL;
-    }
+    ipi_states[cpu_addr] = state;

+S390CPU *s390_cpu_addr2state(uint16_t cpu_addr)
      return ipi_states[cpu_addr];

This is what got us into the link<> discussion last time. If we do

for (i = 0; i < ARRAY_SIZE(ipi_states); i++) {
     name = g_strdup_printf("cpu[%i]", i);
     object_property_add_link(qdev_get_machine(), name, TYPE_S390_CPU,
                              &ipi_states[i], &err);

then we get said /machine/cpu[n] link<> properties, at a QMP level
either returning nothing or the canonical path to the CPU object.

On IRC I didn't get an answer of whether it was being done the above way
because there is infrastructure missing, and a look at object.h now
confirms that suspicion. CC'ing Anthony and Paolo.

Since object_property_add_link() uses a NULL opaque, my idea would be to
add a single setter hook argument passed through as opaque to
object_set_link_property(), which would call it with the old and the new

The purpose would be to avoid growing our own internal setter API, which
is disjoint from the QMP qom-set we are targetting at.

Ok, you lost me :). I must admit my understanding of QOM is still limited. Sorry for not keeping up. Why do we need this new hook? The link would contain a pointer to the correct ipi_states entry right? What are we using opaque for?

-- Jason J. Herne (address@hidden)

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