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Date: Wed, 16 Oct 2013 15:06:27 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] RFC: KVM _CREATE_DEVICE considered harmful?
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To: Christian Borntraeger <christian@borntraeger.net>
Cc: KVM list <kvm@vger.kernel.org>, Gleb Natapov <gleb@redhat.com>, Valgrind Developers <valgrind-developers@lists.sourceforge.net>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Alexander Graf <agraf@suse.de>, Jens Freimann <jfrei@linux.vnet.ibm.com>

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