Re: [PATCH v1 4/5] arm/kvm: add skeleton implementation for userspace SMCCC call handling

[Cornelia Huck <cohuck@redhat.com>]

On Mon, Jun 26 2023, Shaoqin Huang <shahuang@redhat.com> wrote:

> The SMCCC call filtering provide the ability to forward the SMCCC call
> to userspace, so we provide a new option `user-smccc` to enable handling
> SMCCC call in userspace, the default value is off.
>
> And add the skeleton implementation for userspace SMCCC call
> initialization and handling.
>
> Signed-off-by: Shaoqin Huang <shahuang@redhat.com>
> ---
>  docs/system/arm/virt.rst |  4 +++
>  hw/arm/virt.c            | 21 ++++++++++++++++
>  include/hw/arm/virt.h    |  1 +
>  target/arm/kvm.c         | 54 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 80 insertions(+)
>
> diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst
> index 1cab33f02e..ff43d52f04 100644
> --- a/docs/system/arm/virt.rst
> +++ b/docs/system/arm/virt.rst
> @@ -155,6 +155,10 @@ dtb-randomness
>    DTB to be non-deterministic. It would be the responsibility of
>    the firmware to come up with a seed and pass it on if it wants to.
>  
> +user-smccc
> +  Set ``on``/``off`` to enable/disable handling smccc call in userspace
> +  instead of kernel.
> +
>  dtb-kaslr-seed
>    A deprecated synonym for dtb-randomness.
>  
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 9b9f7d9c68..767720321c 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -42,6 +42,7 @@
>  #include "hw/vfio/vfio-amd-xgbe.h"
>  #include "hw/display/ramfb.h"
>  #include "net/net.h"
> +#include "qom/object.h"
>  #include "sysemu/device_tree.h"
>  #include "sysemu/numa.h"
>  #include "sysemu/runstate.h"
> @@ -2511,6 +2512,19 @@ static void virt_set_oem_table_id(Object *obj, const char *value,
>      strncpy(vms->oem_table_id, value, 8);
>  }
>  
> +static bool virt_get_user_smccc(Object *obj, Error **errp)
> +{
> +    VirtMachineState *vms = VIRT_MACHINE(obj);
> +
> +    return vms->user_smccc;
> +}
> +
> +static void virt_set_user_smccc(Object *obj, bool value, Error **errp)
> +{
> +    VirtMachineState *vms = VIRT_MACHINE(obj);
> +
> +    vms->user_smccc = value;
> +}
>  
>  bool virt_is_acpi_enabled(VirtMachineState *vms)
>  {
> @@ -3155,6 +3169,13 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
>                                            "in ACPI table header."
>                                            "The string may be up to 8 bytes in size");
>  
> +    object_class_property_add_bool(oc, "user-smccc",
> +                                   virt_get_user_smccc,
> +                                   virt_set_user_smccc);
> +    object_class_property_set_description(oc, "user-smccc",
> +                                          "Set on/off to enable/disable "
> +                                          "handling smccc call in userspace");
> +
>  }
>  
>  static void virt_instance_init(Object *obj)

This knob pretty much only makes sense for KVM guests, and we'll ignore
it with tcg -- would it make sense to check that we are actually using
KVM before we proceed (like we do for the tcg-only props?)