On Thu, 26 Jun 2014 18:30:16 +0100
Will Deacon <will.deacon@xxxxxxx> wrote:
> kvm_ioctl_create_device currently has knowledge of all the device types
> and their associated ops. This is fairly inflexible when adding support
> for new in-kernel device emulations, so move what we currently have out
> into a table, which can support dynamic registration of ops by new
> drivers for virtual hardware.
>
> I didn't try to port all current drivers over, as it's not always clear
> which initialisation hook the ops should be registered from.
I like the general idea of registering the ops dynamically, some
comments below.
>
> Cc: Gleb Natapov <gleb@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> Cc: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
> Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
> ---
>
> Hi guys,
>
> I've just started writing a virtual IOMMU for the ARM SMMU and figured a
> registration mechanism for kvm_device_ops would be a nice cleanup for
> that.
>
> Will
>
> include/linux/kvm_host.h | 1 +
> include/uapi/linux/kvm.h | 1 +
> virt/kvm/kvm_main.c | 65 ++++++++++++++++++++++++++++--------------------
> 3 files changed, 40 insertions(+), 27 deletions(-)
>
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index e11d8f170a62..3b368166286f 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -949,6 +949,7 @@ struct kvm_device_attr {
> #define KVM_DEV_VFIO_GROUP_DEL 2
> #define KVM_DEV_TYPE_ARM_VGIC_V2 5
> #define KVM_DEV_TYPE_FLIC 6
> +#define KVM_DEV_TYPE_MAX 7
This means we always need to move this value once we introduce a new
kvm device type. Can't you keep it in a dynamic list instead of a
table? We just need to do the lookup during device creation anyway.
>
> /*
> * ioctls for VM fds
> +int kvm_register_device_ops(struct kvm_device_ops *ops, u32 type)
> +{
> + if (type >= KVM_DEV_TYPE_MAX)
> + return -ENOSPC;
> +
> + if (kvm_device_ops_table[type] != NULL)
> + return -EEXIST;
Checking for type collisions would be a bit more expensive with a list,
but I don't think it matters.
> +
> + kvm_device_ops_table[type] = ops;
> + return 0;
> +}
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