Re: [PATCH 2/7] xen: introduce the header file for the Xen 9pfs transport protocol

[Boris Ostrovsky]

On 03/06/2017 04:36 PM, Stefano Stabellini wrote:
> On Mon, 6 Mar 2017, Boris Ostrovsky wrote:
>>> +	uint32_t size;
>>> +	uint8_t id;
>>> +	uint16_t tag;
>> I realize that this is in the spec now and it's probably too late to ask
>> this question but wouldn't it be better if id and tag were swapped? No
>> need to pack and potentially faster access to tag.
> I cannot do anything about it: that struct is defined by the 9pfs
> specification (not the Xen spec, the general 9pfs spec). See:

Oh, I thought it was Xen-specific (because it's described in
9pfs.markdown). Nevermind then.

-boris

>
> https://www.usenix.org/legacy/event/usenix05/tech/freenix/full_papers/hensbergen/hensbergen.pdf
>
>>> +} __attribute__((packed));
>>> +
>>> +#define XEN_9PFS_RING_ORDER 6
>>> +#define XEN_9PFS_RING_SIZE  XEN_FLEX_RING_SIZE(XEN_9PFS_RING_ORDER)
>>> +DEFINE_XEN_FLEX_RING_AND_INTF(xen_9pfs);
>>> +
>>> +#endif