Re: [Qemu-devel] [PATCH v8 4/7] s390x/cpu: Tolerate max_cpus

[Matthew Rosato]

On 03/04/2016 03:05 AM, David Hildenbrand wrote:
>> Once hotplug is enabled, interrupts may come in for CPUs
>> with an address > smp_cpus.  Allocate for this and allow
>> search routines to look beyond smp_cpus.
>>
>> Signed-off-by: Matthew Rosato 
>> ---
>>  hw/s390x/s390-virtio.c | 13 +++--
>>  1 file changed, 7 insertions(+), 6 deletions(-)
>>
>> diff --git a/hw/s390x/s390-virtio.c b/hw/s390x/s390-virtio.c
>> index c501a48..90bc58a 100644
>> --- a/hw/s390x/s390-virtio.c
>> +++ b/hw/s390x/s390-virtio.c
>> @@ -58,15 +58,16 @@
>>  #define S390_TOD_CLOCK_VALUE_MISSING0x00
>>  #define S390_TOD_CLOCK_VALUE_PRESENT0x01
>>
>> -static S390CPU **ipi_states;
>> +static S390CPU **cpu_states;
>>
>>  S390CPU *s390_cpu_addr2state(uint16_t cpu_addr)
>>  {
>> -if (cpu_addr >= smp_cpus) {
>> +if (cpu_addr >= max_cpus) {
>>  return NULL;
>>  }
>>
>> -return ipi_states[cpu_addr];
>> +/* Fast lookup via CPU ID */
>> +return cpu_states[cpu_addr];
>>  }
>>
>>  void s390_init_ipl_dev(const char *kernel_filename,
>> @@ -101,14 +102,14 @@ void s390_init_cpus(MachineState *machine)
>>  machine->cpu_model = "host";
>>  }
>>
>> -ipi_states = g_malloc(sizeof(S390CPU *) * smp_cpus);
>> +cpu_states = g_malloc0(sizeof(S390CPU *) * max_cpus);
>>
>> -for (i = 0; i < smp_cpus; i++) {
>> +for (i = 0; i < max_cpus; i++) {
>>  S390CPU *cpu;
>>
>>  cpu = cpu_s390x_init(machine->cpu_model);
>>
>> -ipi_states[i] = cpu;
>> +cpu_states[i] = cpu;
> 
> This looks wrong (creating all cpus). But the net patch fixes it again.
> 

Ouch.  Definitely wrong, error introduced during patch split.  We
allocate for max_cpus, but should only create smp_cpus cpus during init.

> Can you make this patch a simple rename patch and move the max_cpu stuff into
> the next patch if this makes sense?
> 
> Or simply set the cpu_state for everything above smp_cpus to zero in this 
> patch.

This is done via the gmalloc0.  If I hadn't messed up this loop, the net
result would be the ability to handle > smp_cpus, but nobody will ever
create one (yet).

Matt

Re: [Qemu-devel] [PATCH v8 4/7] s390x/cpu: Tolerate max_cpus

[David Hildenbrand]

> Once hotplug is enabled, interrupts may come in for CPUs
> with an address > smp_cpus.  Allocate for this and allow
> search routines to look beyond smp_cpus.
> 
> Signed-off-by: Matthew Rosato 
> ---
>  hw/s390x/s390-virtio.c | 13 +++--
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/s390x/s390-virtio.c b/hw/s390x/s390-virtio.c
> index c501a48..90bc58a 100644
> --- a/hw/s390x/s390-virtio.c
> +++ b/hw/s390x/s390-virtio.c
> @@ -58,15 +58,16 @@
>  #define S390_TOD_CLOCK_VALUE_MISSING0x00
>  #define S390_TOD_CLOCK_VALUE_PRESENT0x01
> 
> -static S390CPU **ipi_states;
> +static S390CPU **cpu_states;
> 
>  S390CPU *s390_cpu_addr2state(uint16_t cpu_addr)
>  {
> -if (cpu_addr >= smp_cpus) {
> +if (cpu_addr >= max_cpus) {
>  return NULL;
>  }
> 
> -return ipi_states[cpu_addr];
> +/* Fast lookup via CPU ID */
> +return cpu_states[cpu_addr];
>  }
> 
>  void s390_init_ipl_dev(const char *kernel_filename,
> @@ -101,14 +102,14 @@ void s390_init_cpus(MachineState *machine)
>  machine->cpu_model = "host";
>  }
> 
> -ipi_states = g_malloc(sizeof(S390CPU *) * smp_cpus);
> +cpu_states = g_malloc0(sizeof(S390CPU *) * max_cpus);
> 
> -for (i = 0; i < smp_cpus; i++) {
> +for (i = 0; i < max_cpus; i++) {
>  S390CPU *cpu;
> 
>  cpu = cpu_s390x_init(machine->cpu_model);
> 
> -ipi_states[i] = cpu;
> +cpu_states[i] = cpu;

This looks wrong (creating all cpus). But the net patch fixes it again.

Can you make this patch a simple rename patch and move the max_cpu stuff into
the next patch if this makes sense?

Or simply set the cpu_state for everything above smp_cpus to zero in this patch.

Whatever you think makes sense.

>  }
>  }
> 


David

[Qemu-devel] [PATCH v8 4/7] s390x/cpu: Tolerate max_cpus

[Matthew Rosato]

Once hotplug is enabled, interrupts may come in for CPUs
with an address > smp_cpus.  Allocate for this and allow
search routines to look beyond smp_cpus.

Signed-off-by: Matthew Rosato 
---
 hw/s390x/s390-virtio.c | 13 +++--
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/hw/s390x/s390-virtio.c b/hw/s390x/s390-virtio.c
index c501a48..90bc58a 100644
--- a/hw/s390x/s390-virtio.c
+++ b/hw/s390x/s390-virtio.c
@@ -58,15 +58,16 @@
 #define S390_TOD_CLOCK_VALUE_MISSING0x00
 #define S390_TOD_CLOCK_VALUE_PRESENT0x01
 
-static S390CPU **ipi_states;
+static S390CPU **cpu_states;
 
 S390CPU *s390_cpu_addr2state(uint16_t cpu_addr)
 {
-if (cpu_addr >= smp_cpus) {
+if (cpu_addr >= max_cpus) {
 return NULL;
 }
 
-return ipi_states[cpu_addr];
+/* Fast lookup via CPU ID */
+return cpu_states[cpu_addr];
 }
 
 void s390_init_ipl_dev(const char *kernel_filename,
@@ -101,14 +102,14 @@ void s390_init_cpus(MachineState *machine)
 machine->cpu_model = "host";
 }
 
-ipi_states = g_malloc(sizeof(S390CPU *) * smp_cpus);
+cpu_states = g_malloc0(sizeof(S390CPU *) * max_cpus);
 
-for (i = 0; i < smp_cpus; i++) {
+for (i = 0; i < max_cpus; i++) {
 S390CPU *cpu;
 
 cpu = cpu_s390x_init(machine->cpu_model);
 
-ipi_states[i] = cpu;
+cpu_states[i] = cpu;
 }
 }
 
-- 
1.9.1