netdev - Re: [RFC PATCH v2 1/2] net: af_packet support for direct ring access in user space

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Message-ID: <54B538C1.6000500@gmail.com>
Date:	Tue, 13 Jan 2015 07:24:49 -0800
From:	John Fastabend <john.fastabend@...il.com>
To:	Daniel Borkmann <dborkman@...hat.com>
CC:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	netdev@...r.kernel.org, danny.zhou@...el.com,
	nhorman@...driver.com, john.ronciak@...el.com, brouer@...hat.com
Subject: Re: [RFC PATCH v2 1/2] net: af_packet support for direct ring access
 in user space

On 01/13/2015 05:21 AM, Daniel Borkmann wrote:
> On 01/13/2015 01:35 PM, Hannes Frederic Sowa wrote:
>> On Mo, 2015-01-12 at 20:35 -0800, John Fastabend wrote:
> ...
>>> +/* setsockopt takes addr, size ,direction parametner, getsockopt takes
>>> + * iova, size, direction.
>>> + * */
>>> +struct tpacket_dma_mem_region {
>>> +    void *addr;        /* userspace virtual address */
>>> +    __u64 phys_addr;    /* physical address */
>>> +    __u64 iova;        /* IO virtual address used for DMA */
>>> +    unsigned long size;    /* size of region */
>>> +    int direction;        /* dma data direction */
>>> +};
>>
>> Have you tested this with with 32 bit user space and 32 bit kernel, too?
>> I don't have any problem with only supporting 64 bit kernels for this
>> feature, but looking through the code I wonder if we handle the __u64
>> addresses correctly in all situations.

We still need to test/implement this I'm going to guess there is some
more work needed for this to work correctly.

>
> Given this is placed into uapi and transferred via setsockopt(2), this
> would also need some form of compat handling, also for the case of mixed
> environments (e.g. 64 bit kernel, 32 bit user space).

noted, thanks!

-- 
John Fastabend         Intel Corporation
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