Re: [RFC PATCH 3/16]: PVH xen: Add PHYSDEVOP_map_iomem

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

On Thu, Jan 24, 2013 at 05:03:50PM -0800, Mukesh Rathor wrote:
> On Thu, 24 Jan 2013 15:06:29 +0000
> Tim Deegan <tim@xen.org> wrote:
> 
> > At 17:32 -0800 on 11 Jan (1357925563), Mukesh Rathor wrote:
> >DEFINE_XEN_GUEST_HANDLE(physdev_dbgp_op_t);
> > >  
> > > + 
> > > +#define PHYSDEVOP_map_iomem        30
> > > +struct physdev_map_iomem {
> > > +    /* IN */
> > > +    unsigned long first_gfn;
> > > +    unsigned long first_mfn;
> > > +    unsigned int nr_mfns;
> > > +    unsigned int add_mapping;        /* 1 == add mapping;  0 ==
> > > unmap */ +
> > > +};
> > > +typedef struct physdev_map_iomem physdev_map_iomem_t;
> > > +DEFINE_XEN_GUEST_HANDLE(physdev_map_iomem_t);
> > > +
> > 
> > This needs documentation.  Also, the arguemnts should be explicitly
> > sized to avoid compat difficulties. 
> > 
> > Tim.
> 
> Done:
> 
> /* Map given gfns to mfns where mfns are part of IO space. */
> #define PHYSDEVOP_map_iomem        30
> struct physdev_map_iomem {
>     /* IN */
>     uint64_t first_gfn;
>     uint64_t first_mfn;
>     uint32_t nr_mfns;
>     uint32_t add_mapping;        /* 1 == add mapping;  0 == unmap */
> 
> };

Which is BTW what the Linux tree already has.

Perhaps the 'add_mapping' should be just called 'flags'
and have two #defines?

It is also has a bit of an issue when you use __packed__ - that is it
will shrink from 32 bytes down to 24 bytes. Perhaps we should make this
hypercall be:

	uint64_t first_gfn
	uint64_t first_mfn;
	uint32_t nr_mfns;
	uint32_t flags;
	uint64_t _pad;

and then it is a nice 32 bytes long?

> 
> 
> thanks,
> Mukesh
> 
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