Re: [Qemu-devel] [RFC 5/6] hw/arm/virt: support kvm_type property

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Eric Auger (eric.auger@redhat.com) wrote:
> The kvm-type property currently is used to pass
> a user parameter to KVM_CREATE_VM. This matches
> the way KVM/ARM expects to pass the max_vm_phys_shift
> parameter.
> 
> This patch adds the support or the kvm-type property in
> machvirt and also implements the machine class kvm_type()
> callback so that it either returns the kvm-type value
> provided by the user or returns the max_vm_phys_shift
> exposed by KVM.
> 
> for instance, the usespace can use the following option to
> instantiate a 42b IPA guest: -machine kvm-type=42

Without saying if this is better or worse, it is different from x86,
where we have the number of physical address bits as a -cpu parameter
rather than a machine parameter, e.g.

   qemu-system-x86_64 -M pc,accel=kvm -cpu SandyBridge,phys-bits=36
or
   qemu-system-x86_64 -M pc,accel=kvm -cpu SandyBridge,host-phys-bits=true

our machine types can override the default value though.

One other complication (that I don't know if it applies to ARM) is that
TCG only supports phys-bits=40, so we refuse a TCG run with an
explicitly set phys-bits!=40.

Dave

> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> ---
>  hw/arm/virt.c         | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  include/hw/arm/virt.h |  1 +
>  2 files changed, 45 insertions(+)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index dd92ab9..1700556 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1585,6 +1585,21 @@ static void virt_set_iommu(Object *obj, const char *value, Error **errp)
>      }
>  }
>  
> +static char *virt_get_kvm_type(Object *obj, Error **errp)
> +{
> +    VirtMachineState *vms = VIRT_MACHINE(obj);
> +
> +    return g_strdup(vms->kvm_type);
> +}
> +
> +static void virt_set_kvm_type(Object *obj, const char *value, Error **errp)
> +{
> +    VirtMachineState *vms = VIRT_MACHINE(obj);
> +
> +    g_free(vms->kvm_type);
> +    vms->kvm_type = g_strdup(value);
> +}
> +
>  static CpuInstanceProperties
>  virt_cpu_index_to_props(MachineState *ms, unsigned cpu_index)
>  {
> @@ -1646,6 +1661,31 @@ static HotplugHandler *virt_machine_get_hotplug_handler(MachineState *machine,
>      return NULL;
>  }
>  
> +static int virt_kvm_type(MachineState *ms, const char *type_str)
> +{
> +    int max_vm_phys_shift, ret = 0;
> +    uint64_t type;
> +
> +    if (!type_str) {
> +        max_vm_phys_shift = kvm_get_max_vm_phys_shift(ms);
> +        if (max_vm_phys_shift < 0) {
> +            goto out;
> +        }
> +    } else {
> +        type = g_ascii_strtoll(type_str, NULL, 0);
> +        type &= 0xFF;
> +        max_vm_phys_shift = (int)type;
> +        if (max_vm_phys_shift < 40 || max_vm_phys_shift > 52) {
> +            warn_report("valid kvm-type type values are within [40, 52]:"
> +                        " option is ignored and VM is created with 40b IPA");
> +            goto out;
> +        }
> +    }
> +    ret = max_vm_phys_shift;
> +out:
> +    return ret;
> +}
> +
>  static void virt_machine_class_init(ObjectClass *oc, void *data)
>  {
>      MachineClass *mc = MACHINE_CLASS(oc);
> @@ -1668,6 +1708,7 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
>      mc->cpu_index_to_instance_props = virt_cpu_index_to_props;
>      mc->default_cpu_type = ARM_CPU_TYPE_NAME("cortex-a15");
>      mc->get_default_cpu_node_id = virt_get_default_cpu_node_id;
> +    mc->kvm_type = virt_kvm_type;
>      assert(!mc->get_hotplug_handler);
>      mc->get_hotplug_handler = virt_machine_get_hotplug_handler;
>      hc->plug = virt_machine_device_plug_cb;
> @@ -1756,6 +1797,9 @@ static void virt_3_0_instance_init(Object *obj)
>                                      "Valid values are none and smmuv3",
>                                      NULL);
>  
> +    object_property_add_str(obj, "kvm-type",
> +                            virt_get_kvm_type, virt_set_kvm_type, NULL);
> +
>      vms->memmap = a15memmap;
>      vms->irqmap = a15irqmap;
>  }
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 4ac7ef6..2674ce7 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -118,6 +118,7 @@ typedef struct {
>      uint32_t msi_phandle;
>      uint32_t iommu_phandle;
>      int psci_conduit;
> +    char *kvm_type;
>  } VirtMachineState;
>  
>  #define TYPE_VIRT_MACHINE   MACHINE_TYPE_NAME("virt")
> -- 
> 2.5.5
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK