Re: [Xen-devel] [PATCH 2/9] Linux kernel infrastructure for Xen Share access

["Mike D. Day" <ncmike@xxxxxxxxxx>]

Rusty Russell wrote:

> The entire hypercall interface is arch-wrapped, which is probably
> overkill, but I wasn't entirely sure of the needs of non-x86
> architectures.  Some of this should almost certainly be in common code.
>
> diff -r 6d476981e3a5 -r 07a00d96357d 
> linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/share.h

> +struct xen_share *create_share(share_ref_t share_ref, unsigned pages)
<snip>

> +
> +       prot = __pgprot(_PAGE_PRESENT|_PAGE_RW|_PAGE_DIRTY|_PAGE_ACCESSED);
> +       err = direct_kernel_remap_pfn_range((unsigned long)vma->addr,
> +                                           share_ref, pages * PAGE_SIZE,
> +                                           prot, DOMID_SELF);
Using share_ref as the 2nd parameter to remap_pfn_range it becomes clear 
that share_ref is really a page frame number. This is also made clear in 
  xen/arch/x86/share.c.
My question is: is it useful to abstract the share reference when it is 
always going to be a page number? Is there any architecture where it 
wouldn't be feasible to refer to a share by page number?
Really this is just a readability issue.

Mike


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