Re: [Qemu-devel] [PATCH v1 1/2] xlnx-zynqmp: Properly support the smp command line option

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Nov 07, 2017 at 10:59:39AM -0800, Alistair Francis wrote:
> Allow the -smp command line option to control the number of CPUs we
> create.
> 
> Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
> ---
> 
>  hw/arm/xlnx-zcu102.c |  3 ++-
>  hw/arm/xlnx-zynqmp.c | 26 ++++++++++++++++----------
>  2 files changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/arm/xlnx-zcu102.c b/hw/arm/xlnx-zcu102.c
> index e2d15a1c9d..7ec03dad42 100644
> --- a/hw/arm/xlnx-zcu102.c
> +++ b/hw/arm/xlnx-zcu102.c
> @@ -235,7 +235,8 @@ static void xlnx_zcu102_machine_class_init(ObjectClass *oc, void *data)
>  {
>      MachineClass *mc = MACHINE_CLASS(oc);
>  
> -    mc->desc = "Xilinx ZynqMP ZCU102 board";
> +    mc->desc = "Xilinx ZynqMP ZCU102 board with 4xA53s and 2xR5s based on " \
> +               "the value of smp";
>      mc->init = xlnx_zcu102_init;
>      mc->block_default_type = IF_IDE;
>      mc->units_per_default_bus = 1;
> diff --git a/hw/arm/xlnx-zynqmp.c b/hw/arm/xlnx-zynqmp.c
> index d4b6560194..c707c66322 100644
> --- a/hw/arm/xlnx-zynqmp.c
> +++ b/hw/arm/xlnx-zynqmp.c
> @@ -98,8 +98,9 @@ static void xlnx_zynqmp_create_rpu(XlnxZynqMPState *s, const char *boot_cpu,
>  {
>      Error *err = NULL;
>      int i;
> +    int num_rpus = MIN(smp_cpus - XLNX_ZYNQMP_NUM_APU_CPUS, XLNX_ZYNQMP_NUM_RPU_CPUS);
>  
> -    for (i = 0; i < XLNX_ZYNQMP_NUM_RPU_CPUS; i++) {
> +    for (i = 0; i < num_rpus; i++) {
>          char *name;
>  
>          object_initialize(&s->rpu_cpu[i], sizeof(s->rpu_cpu[i]),
> @@ -132,8 +133,9 @@ static void xlnx_zynqmp_init(Object *obj)
>  {
>      XlnxZynqMPState *s = XLNX_ZYNQMP(obj);
>      int i;
> +    int num_apus = MIN(smp_cpus, XLNX_ZYNQMP_NUM_APU_CPUS);
>  
> -    for (i = 0; i < XLNX_ZYNQMP_NUM_APU_CPUS; i++) {
> +    for (i = 0; i < num_apus; i++) {
>          object_initialize(&s->apu_cpu[i], sizeof(s->apu_cpu[i]),
>                            "cortex-a53-" TYPE_ARM_CPU);
>          object_property_add_child(obj, "apu-cpu[*]", OBJECT(&s->apu_cpu[i]),
> @@ -182,6 +184,7 @@ static void xlnx_zynqmp_realize(DeviceState *dev, Error **errp)
>      MemoryRegion *system_memory = get_system_memory();
>      uint8_t i;
>      uint64_t ram_size;
> +    int num_apus = MIN(smp_cpus, XLNX_ZYNQMP_NUM_APU_CPUS);
>      const char *boot_cpu = s->boot_cpu ? s->boot_cpu : "apu-cpu[0]";
>      ram_addr_t ddr_low_size, ddr_high_size;
>      qemu_irq gic_spi[GIC_NUM_SPI_INTR];
> @@ -233,10 +236,10 @@ static void xlnx_zynqmp_realize(DeviceState *dev, Error **errp)
>  
>      qdev_prop_set_uint32(DEVICE(&s->gic), "num-irq", GIC_NUM_SPI_INTR + 32);
>      qdev_prop_set_uint32(DEVICE(&s->gic), "revision", 2);
> -    qdev_prop_set_uint32(DEVICE(&s->gic), "num-cpu", XLNX_ZYNQMP_NUM_APU_CPUS);
> +    qdev_prop_set_uint32(DEVICE(&s->gic), "num-cpu", num_apus);
>  
>      /* Realize APUs before realizing the GIC. KVM requires this.  */
> -    for (i = 0; i < XLNX_ZYNQMP_NUM_APU_CPUS; i++) {
> +    for (i = 0; i < num_apus; i++) {
>          char *name;
>  
>          object_property_set_int(OBJECT(&s->apu_cpu[i]), QEMU_PSCI_CONDUIT_SMC,
> @@ -292,7 +295,7 @@ static void xlnx_zynqmp_realize(DeviceState *dev, Error **errp)
>          }
>      }
>  
> -    for (i = 0; i < XLNX_ZYNQMP_NUM_APU_CPUS; i++) {
> +    for (i = 0; i < num_apus; i++) {
>          qemu_irq irq;
>  
>          sysbus_connect_irq(SYS_BUS_DEVICE(&s->gic), i,
> @@ -307,11 +310,14 @@ static void xlnx_zynqmp_realize(DeviceState *dev, Error **errp)
>      }
>  
>      if (s->has_rpu) {
> -        xlnx_zynqmp_create_rpu(s, boot_cpu, &err);
> -        if (err) {
> -            error_propagate(errp, err);
> -            return;
> -        }
> +        info_report("The 'has_rpu' property is no longer required, to use the "
> +                    "RPUs just use -smp 6.");
> +    }

Is "-global driver=xlnx,,zynqmp,property=has_rpu,value=on"
without an explicit -smp option supposed to be a supported
configuration?

0) On current master, we have this:

  $ ./aarch64-softmmu/qemu-system-aarch64 -machine xlnx-zcu102 -global driver=xlnx,,zynqmp,property=has_rpu,value=on
  **
  ERROR:/home/ehabkost/rh/proj/virt/qemu/tcg/tcg.c:538:tcg_register_thread: assertion failed: (n < max_cpus)
  Aborted (core dumped)

1) With your patch we have this:

  $ ./aarch64-softmmu/qemu-system-aarch64 -machine xlnx-zcu102 -global driver=xlnx,,zynqmp,property=has_rpu,value=on -monitor stdio
  QEMU 2.10.50 monitor - type 'help' for more information
  (qemu) qemu-system-aarch64: info: The 'has_rpu' property is no longer required, to use the RPUs just use -smp 6.
  (qemu) info cpus
  * CPU #0: thread_id=1662
  (qemu) 

2) With your patch plus Emilio's original min_cpus/default_cpus
proposal[1], we have this:

  $ ./aarch64-softmmu/qemu-system-aarch64 -machine xlnx-zcu102 -global driver=xlnx,,zynqmp,property=has_rpu,value=on -monitor stdio
  QEMU 2.10.50 monitor - type 'help' for more information
  (qemu) qemu-system-aarch64: info: The 'has_rpu' property is no longer required, to use the RPUs just use -smp 6.
  (qemu) info cpus
  * CPU #0: thread_id=7112
    CPU #1: (halted) thread_id=7113
    CPU #2: (halted) thread_id=7114
    CPU #3: (halted) thread_id=7115
  (qemu)

3) With Emilio's max_additional_cpus proposal[2], we have this:

  $ ./aarch64-softmmu/qemu-system-aarch64 -machine xlnx-zcu102 -global driver=xlnx,,zynqmp,property=has_rpu,value=on -monitor stdio
  QEMU 2.10.50 monitor - type 'help' for more information
  (qemu) info cpus
  * CPU #0: thread_id=4045
    CPU #1: (halted) thread_id=4046
    CPU #2: (halted) thread_id=4047
    CPU #3: (halted) thread_id=4048
    CPU #4: (halted) thread_id=4049
    CPU #5: (halted) thread_id=4050
  (qemu) 


Which option is preferred?  I like option #2 because it's
simpler, but I would like to confirm this is really the intended
behavior.


[1] https://mid.mail-archive.com/1509734853-3014-1-git-send-email-cota@braap.org
[2] https://mid.mail-archive.com/20171106215454.GB2152@flamenco


> +
> +    xlnx_zynqmp_create_rpu(s, boot_cpu, &err);
> +    if (err) {
> +        error_propagate(errp, err);
> +        return;
>      }
>  
>      if (!s->boot_cpu_ptr) {
> -- 
> 2.11.0
> 

-- 
Eduardo