Re: [RFC ABI V2 5/8] RDMA/core: Add new ioctl interface

[Matan Barak <matanb-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>]

On 20/07/2016 04:25, Christoph Lameter wrote:
> On Tue, 19 Jul 2016, Matan Barak wrote:
>
>> diff --git a/include/uapi/rdma/rdma_user_ioctl.h b/include/uapi/rdma/rdma_user_ioctl.h
>> index 5c1117a..f6927fc 100644
>> --- a/include/uapi/rdma/rdma_user_ioctl.h
>> +++ b/include/uapi/rdma/rdma_user_ioctl.h
>> @@ -42,6 +42,29 @@
>>   */
>>  #define IB_IOCTL_MAGIC			RDMA_IOCTL_MAGIC
>>
>> +#define RDMA_VERBS_IOCTL \
>> +	_IOWR(RDMA_IOCTL_MAGIC, 1, struct ib_uverbs_ioctl_hdr)
>> +
>> +#define RDMA_DIRECT_IOCTL \
>> +	_IOWR(RDMA_IOCTL_MAGIC, 2, struct ib_uverbs_ioctl_hdr)
>> +
>> +struct ib_uverbs_attr {
>> +	__u16 attr_id;		/* command specific type attribute */
>> +	__u16 len;		/* NA for idr */
>> +	__u32 reserved;
>> +	 __u64 ptr_idr;		/* ptr typeo command/idr handle */
>> +};
>> +
>> +struct ib_uverbs_ioctl_hdr {
>> +	__u16 length;
>> +	__u16 flags;
>> +	__u16 object_type;
>> +	__u16 driver_id;
>
> driver id??? I would have expected that the driver to be used is
> already selected through the file handle as passed to the ioctl.
>

If I recall, Jason proposed that. I think the main reason here is for 
strace and debugging. Since the ABI is now driver specific, this helps 
you parse the structs via strace.

> Having the ability to issue ioctls to multiple drivers via a
> single file handle is unusual and will likely trigger security concerns.
> In particular various access mechanisms rely on policing access through
> file handles.
>

This is actually an ongoing discussion we have in the OFVWG. The benefit 
of unifying rdma-cm and uverbs is that sharing objects (and opening a 
device through rdma-cm and pass it to user-space) becomes easier. That 
means that security should be handled via selinux.

> I guess we have a good reason for doing so? If so then please document
> that somewhere. Or did I not see that?
>
>

The current v2 approach only adds the driver_id for information and 
strace only. I would really like to hear your insights about using a 
single file (rdma_uapi) vs multiple files as we have today.

> +	 __u16 action; > +	__u16 num_attrs;
>> +	struct ib_uverbs_attr  attrs[0];
>> +};
>> +
>>  /* Legacy part
>>   * !!!! NOTE: It uses the same command index as VERBS
>>   */
>>

Matan
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