Re: [Qemu-devel] [PATCH v1 08/11] s390x: allow only 1 CPU with TCG

[David Hildenbrand]

On 31.08.2017 17:07, Cornelia Huck wrote:
> On Thu, 31 Aug 2017 17:03:21 +0200
> David Hildenbrand <da...@redhat.com> wrote:
> 
>> On 31.08.2017 16:41, Cornelia Huck wrote:
>>> On Wed, 30 Aug 2017 19:05:58 +0200
>>> David Hildenbrand <da...@redhat.com> wrote:
>>>   
>>>> Specifying more than 1 CPU (e.g. -smp 5) leads to SIGP errors (the
>>>> guest tries to bring these CPUs up but fails), because we don't support
>>>> multiple CPUs on s390x under TCG.
>>>>
>>>> Let's bail out if more than 1 are specified, so we don't raise people's
>>>> hope.
>>>>
>>>> Signed-off-by: David Hildenbrand <da...@redhat.com>
>>>> ---
>>>>  hw/s390x/s390-virtio-ccw.c | 6 ++++++
>>>>  1 file changed, 6 insertions(+)
>>>>
>>>> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
>>>> index 7754e3eaf9..eff96808c4 100644
>>>> --- a/hw/s390x/s390-virtio-ccw.c
>>>> +++ b/hw/s390x/s390-virtio-ccw.c
>>>> @@ -23,6 +23,7 @@
>>>>  #include "hw/s390x/css.h"
>>>>  #include "virtio-ccw.h"
>>>>  #include "qemu/config-file.h"
>>>> +#include "qemu/error-report.h"
>>>>  #include "s390-pci-bus.h"
>>>>  #include "hw/s390x/storage-keys.h"
>>>>  #include "hw/s390x/storage-attributes.h"
>>>> @@ -56,6 +57,11 @@ static void s390_init_cpus(MachineState *machine)
>>>>      if (machine->cpu_model == NULL) {
>>>>          machine->cpu_model = s390_default_cpu_model_name();
>>>>      }
>>>> +    if (tcg_enabled() && max_cpus > 1) {
>>>> +        error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
>>>> +                     "supported by TCG (1) on s390x", max_cpus);  
>>>
>>> Make this a #define, so we can just flip the switch when smp support is
>>> ready?  
>>
>> As an alternative: yield a warning?
> 
> If we know that this can't work, it makes sense to stop immediately, no?

Hmm, like that than?

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 18ed0c57e3..dae848fa5f 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -23,6 +23,7 @@
 #include "hw/s390x/css.h"
 #include "virtio-ccw.h"
 #include "qemu/config-file.h"
+#include "qemu/error-report.h"
 #include "s390-pci-bus.h"
 #include "hw/s390x/storage-keys.h"
 #include "hw/s390x/storage-attributes.h"
@@ -56,6 +57,12 @@ static void s390_init_cpus(MachineState *machine)
     if (machine->cpu_model == NULL) {
         machine->cpu_model = s390_default_cpu_model_name();
     }
+    if (tcg_enabled() && max_cpus > S390_TCG_MAX_CPUS) {
+        error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
+                     "supported by TCG (%d) on s390x", max_cpus,
+                     S390_TCG_MAX_CPUS);
+        exit(1);
+    }

     ms->cpus = g_new0(S390CPU *, max_cpus);

diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index 7ed9103b33..4e1de2102d 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -210,6 +210,8 @@ static inline S390CPU
*s390_env_get_cpu(CPUS390XState *env)

 #define ENV_OFFSET offsetof(S390CPU, env)

+#define S390_TCG_MAX_CPUS 1
+
 #ifndef CONFIG_USER_ONLY
 extern const struct VMStateDescription vmstate_s390_cpu;
 #endif


-- 

Thanks,

David