lkml.org 
[lkml]   [2012]   [Oct]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 1/6] xen/pvh: Support ParaVirtualized Hardware extensions.
From
Date
On Tue, 2012-10-23 at 15:07 +0100, Konrad Rzeszutek Wilk wrote:
> > +/*
> > + * Unmaps the page appearing at a particular GPFN from the specified guest's
> > + * pseudophysical address space.
> > + * arg == addr of xen_remove_from_physmap_t.
> > + */
> > +#define XENMEM_remove_from_physmap 15
> > +struct xen_remove_from_physmap {
> > + /* Which domain to change the mapping for. */
> > + domid_t domid;
> > +
> > + /* GPFN of the current mapping of the page. */
> > + xen_pfn_t gpfn;
> > +};
>
> I just realized that this a bit of unfortunate. We end up
> with on 64-bit with this layout:
>
> {
> 0->1 [domid]
> 2->7 [nothing]
> 8->16 [gpfn]
>
> }
>
> which if one were to do a 32-bit build you would get:
> {
> 0->1 [domid]
> 2->3 [nothing]
> 4->7 [gpfn]
> }
> which means another compat layer in Xen.

A relatively simple one, but yes.

> So I think it makes sense to modify this to be 32 and 64-bit
> clean, something like this:

That works.
We could just swap the domid and gpfn members around, although that
ordering reads a bit unnaturally.

>
> {
> domid_t domid;
> u8 pad[6];
> xen_pfn_t gpfn;
> /* xen_pfn_t under 32-bit x86 is 4 bytes, so extend it */
> #ifdef CONFIG_X86_32
> __u8 pad1[4];
> #endif
> }
>
> that way the structure is exactly the same size and the offsets
> align.
>
> Mukesh, you OK with that?




\
 
 \ /
  Last update: 2012-10-24 12:01    [W:0.079 / U:0.836 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site