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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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:

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
> 

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