Re: [PATCH] sgx: Move sgx object from /machine/unattached to /machine

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Jan 12, 2022 at 11:55:17AM -0500, Yang Zhong wrote:
> When Libvirt start, it get the vcpu's unavailable-features from
> /machine/unattached/device[0] path by qom-get command, but in SGX
> guest, since the sgx-epc virtual device is initialized before VCPU
> creation(virtual sgx need set the virtual EPC info in the cpuid). This
> /machine/unattached/device[0] is occupied by sgx-epc device, which
> fail to get the unvailable-features from /machine/unattached/device[0].

If libvirt decides to enable SGX in a VM, then surely it knows
that it should just query /machine/unattached/device[1] to get
the CPU features instead. Why do we need to do anything in QEMU ?

> 
> This patch make one new /machine/sgx object to avoid this issue.
> (qemu) qom-list /machine/unattached/
> device[0] (child<host-x86_64-cpu>)
> 
> (qemu) qom-list /machine/sgx
> device[0] (child<sgx-epc>)
> 
> Signed-off-by: Yang Zhong <yang.zhong@intel.com>
> ---
>  hw/core/qdev.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 84f3019440..4154eef0d8 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -497,7 +497,7 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
>      NamedClockList *ncl;
>      Error *local_err = NULL;
>      bool unattached_parent = false;
> -    static int unattached_count;
> +    static int unattached_count, sgx_count;
>  
>      if (dev->hotplugged && !dc->hotpluggable) {
>          error_setg(errp, QERR_DEVICE_NO_HOTPLUG, object_get_typename(obj));
> @@ -509,7 +509,15 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
>              goto fail;
>          }
>  
> -        if (!obj->parent) {
> +        if (!obj->parent && !strcmp(object_get_typename(obj), "sgx-epc")) {
> +            gchar *name = g_strdup_printf("device[%d]", sgx_count++);
> +
> +            object_property_add_child(container_get(qdev_get_machine(),
> +                                                    "/sgx"),
> +                                      name, obj);
> +            unattached_parent = true;
> +            g_free(name);

The qdev.c file is part of our generic object code. It should not
contain any code that is tied to very specific object types like
this.

> +        } else if (!obj->parent) {
>              gchar *name = g_strdup_printf("device[%d]", unattached_count++);
>  
>              object_property_add_child(container_get(qdev_get_machine(),

Regards,
Daniel
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