Re: [Xen-devel] [PATCH] introduce grant copy for user land

[Thanos Makatos <thanos.makatos@xxxxxxxxxx>]

> The arbitrary limitations in number of ops and page alignment should be
> removed.  I think both can be removed relatively easily by consuming page
> aligned chunks of segments and doign the hypercall when a batch of ops is
> filled.

Wouldn't this lead to multiple calls to gnttab_batch_copy(), potentially 
hurting performance?

> > +#define IOCTL_GNTDEV_GRANT_COPY \
> > +_IOC(_IOC_NONE, 'G', 8, sizeof(struct ioctl_gntdev_grant_copy))
> > +struct ioctl_gntdev_grant_copy {
> > +   /*
> > +    * copy direction: 0 to copy to guest, 1 to copy from guest
> > +    */
> > +   int dir;
> 
> I think this dir should be per-segment and use the GNTCPY_source_gref and
> GNTCOPY_dest_gref flags, since per-op direction is what the hypercall
> provides.

OK.

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