[Qemu-devel] [PATCH v2] target/s390x/kvm: Officially require at least kernel 3.15

[Thomas Huth <thuth@redhat.com>]

Since QEMU v2.10, the KVM acceleration does not work on older kernels
anymore since the code accidentally requires the KVM_CAP_DEVICE_CTRL
capability now - it should have been optional instead.
Instead of fixing the bug, we asked in the ChangeLog of QEMU 2.11 - 3.0
that people should speak up if they still need support of QEMU running
with KVM on older kernels, but seems like nobody really complained.
Thus let's make this official now and turn it into a proper error
message, telling the users to use at least kernel 3.15 now.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 v2: Remove also the entry in trace-events

 hw/intc/s390_flic_kvm.c | 6 ------
 hw/intc/trace-events    | 1 -
 target/s390x/kvm.c      | 7 +++++++
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/hw/intc/s390_flic_kvm.c b/hw/intc/s390_flic_kvm.c
index 819aa5e198..cedccba8a9 100644
--- a/hw/intc/s390_flic_kvm.c
+++ b/hw/intc/s390_flic_kvm.c
@@ -589,12 +589,6 @@ static void kvm_s390_flic_realize(DeviceState *dev, Error **errp)
         goto fail;
     }
     flic_state->fd = -1;
-    if (!kvm_check_extension(kvm_state, KVM_CAP_DEVICE_CTRL)) {
-        error_setg_errno(&errp_local, errno, "KVM is missing capability"
-                         " KVM_CAP_DEVICE_CTRL");
-        trace_flic_no_device_api(errno);
-        goto fail;
-    }
 
     cd.type = KVM_DEV_TYPE_FLIC;
     ret = kvm_vm_ioctl(kvm_state, KVM_CREATE_DEVICE, &cd);
diff --git a/hw/intc/trace-events b/hw/intc/trace-events
index 90c9d07c1a..719f46b516 100644
--- a/hw/intc/trace-events
+++ b/hw/intc/trace-events
@@ -75,7 +75,6 @@ xics_ics_simple_eoi(int nr) "ics_eoi: irq 0x%x"
 
 # s390_flic_kvm.c
 flic_create_device(int err) "flic: create device failed %d"
-flic_no_device_api(int err) "flic: no Device Contral API support %d"
 flic_reset_failed(int err) "flic: reset failed %d"
 
 # s390_flic.c
diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index cea71ac7c3..97a662ad0e 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -316,6 +316,13 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
     MachineClass *mc = MACHINE_GET_CLASS(ms);
 
     mc->default_cpu_type = S390_CPU_TYPE_NAME("host");
+
+    if (!kvm_check_extension(kvm_state, KVM_CAP_DEVICE_CTRL)) {
+        error_report("KVM is missing capability KVM_CAP_DEVICE_CTRL - "
+                     "please use kernel 3.15 or newer");
+        return -1;
+    }
+
     cap_sync_regs = kvm_check_extension(s, KVM_CAP_SYNC_REGS);
     cap_async_pf = kvm_check_extension(s, KVM_CAP_ASYNC_PF);
     cap_mem_op = kvm_check_extension(s, KVM_CAP_S390_MEM_OP);
-- 
2.18.1