Re: [Qemu-devel] RFC: KVM _CREATE_DEVICE considered harmful?

[Paolo Bonzini]

Il 16/10/2013 14:59, Christian Borntraeger ha scritto:
> 
> Now, newer KVMs have the ability to create subdevices of a KVM guest (e.g. an 
> in kernel
> kvm interrupt controller) with the following ioctl:
> 
> #define KVM_CREATE_DEVICE         _IOWR(KVMIO,  0xe0, struct 
> kvm_create_device)
> 
> qemu can then work on these devices with the ioctls 
> 
> /* ioctls for fds returned by KVM_CREATE_DEVICE */
> #define KVM_SET_DEVICE_ATTR       _IOW(KVMIO,  0xe1, struct kvm_device_attr)
> #define KVM_GET_DEVICE_ATTR       _IOW(KVMIO,  0xe2, struct kvm_device_attr)
> #define KVM_HAS_DEVICE_ATTR       _IOW(KVMIO,  0xe3, struct kvm_device_attr)
> 
> struct kvm_device_attr {
>         __u32   flags;          /* no flags currently defined */
>         __u32   group;          /* device-defined */
>         __u64   attr;           /* group-defined */
>         __u64   addr;           /* userspace address of attr data */
> };

Would it work to simply add an "__u64 size;" field to kvm_device_attr,
that is filled on exit by KVM_GET/HAS_DEVICE_ADDR, and filled on entry
to KVM_SET_DEVICE_ADDR?

Paolo