Re: [RFC PATCH 1/4] confidential guest support: Add kvm_init() and kvm_reset() in class

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

On Tue, Feb 06, 2024 at 03:28:49AM -0500, Xiaoyao Li wrote:
> Different confidential VMs in different architectures all have the same
> needs to do their specific initialization (and maybe resetting) stuffs
> with KVM. Currently each of them exposes individual *_kvm_init()
> functions and let machine code or kvm code to call it.
> 
> To make it more object oriented, add two virtual functions, kvm_init()
> and kvm_reset() in ConfidentialGuestSupportClass, and expose two helpers
> functions for invodking them.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  include/exec/confidential-guest-support.h | 42 ++++++++++++++++++++++-
>  1 file changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/include/exec/confidential-guest-support.h b/include/exec/confidential-guest-support.h
> index ba2dd4b5dfc4..ff0bfb26ad7a 100644
> --- a/include/exec/confidential-guest-support.h
> +++ b/include/exec/confidential-guest-support.h
> @@ -23,7 +23,10 @@
>  #include "qom/object.h"
>  
>  #define TYPE_CONFIDENTIAL_GUEST_SUPPORT "confidential-guest-support"
> -OBJECT_DECLARE_SIMPLE_TYPE(ConfidentialGuestSupport, CONFIDENTIAL_GUEST_SUPPORT)
> +OBJECT_DECLARE_TYPE(ConfidentialGuestSupport,
> +                    ConfidentialGuestSupportClass,
> +                    CONFIDENTIAL_GUEST_SUPPORT)
> +
>  
>  struct ConfidentialGuestSupport {
>      Object parent;
> @@ -55,8 +58,45 @@ struct ConfidentialGuestSupport {
>  
>  typedef struct ConfidentialGuestSupportClass {
>      ObjectClass parent;
> +
> +    int (*kvm_init)(ConfidentialGuestSupport *cgs, Error **errp);
> +    int (*kvm_reset)(ConfidentialGuestSupport *cgs, Error **errp);
>  } ConfidentialGuestSupportClass;
>  
> +static inline int confidential_guest_kvm_init(ConfidentialGuestSupport *cgs,
> +                                              Error **errp)
> +{
> +    ConfidentialGuestSupportClass *klass;
> +
> +    if (!cgs) {
> +        return 0;
> +    }

Typically I would expect any class/object methods to mandate a non-NULL
class/instance pointer.

IOW, the caller would generally be expected to check NULL and not
call this method in that case.

> +
> +    klass = CONFIDENTIAL_GUEST_SUPPORT_GET_CLASS(cgs);
> +    if (klass->kvm_init) {
> +        return klass->kvm_init(cgs, errp);
> +    }
> +
> +    return 0;
> +}
> +
> +static inline int confidential_guest_kvm_reset(ConfidentialGuestSupport *cgs,
> +                                               Error **errp)
> +{
> +    ConfidentialGuestSupportClass *klass;
> +
> +    if (!cgs) {
> +        return 0;
> +    }
> +
> +    klass = CONFIDENTIAL_GUEST_SUPPORT_GET_CLASS(cgs);
> +    if (klass->kvm_reset) {
> +        return klass->kvm_reset(cgs, errp);
> +    }
> +
> +    return 0;
> +}
> +
>  #endif /* !CONFIG_USER_ONLY */
>  
>  #endif /* QEMU_CONFIDENTIAL_GUEST_SUPPORT_H */
> -- 
> 2.34.1
> 

With regards,
Daniel
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