Re: [Xen-devel] [PATCH RFC 2/2] x86/mm: PG_translate implies PG_refcounts

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Aug 24, 2017 at 11:02:33AM +0100, Tim Deegan wrote:
> At 16:58 +0100 on 23 Aug (1503507504), Wei Liu wrote:
> > After 404595352 ("x86/paging: Enforce PG_external == PG_translate ==
> > PG_refcounts"), PG_refcounts and PG_translate always need to be set
> > together.
> > 
> > Squash PG_refcounts to simplify code. All calls paging_mode_refcounts
> > are replaced by calls to paging_mode_translate.
> 
> Would it be a good idea to merge all three and have only PG_external?
> 

My reverse-engineering is that when PV guest is migrated it has
PG_external and (the new) PG_translate.

I would be happy to squash all three into one if you tell me I'm wrong.
:-)

> > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> 
> Acked-by: Tim Deegan <tim@xxxxxxx>
> 
> with one adjustment:
> 
> >  /* common paging mode bits */
> >  #define PG_mode_shift  10 
> > -/* Refcounts based on shadow tables instead of guest tables */
> > -#define PG_refcounts   (XEN_DOMCTL_SHADOW_ENABLE_REFCOUNT << PG_mode_shift)
> >  /* Enable log dirty mode */
> >  #define PG_log_dirty   (XEN_DOMCTL_SHADOW_ENABLE_LOG_DIRTY << 
> > PG_mode_shift)
> >  /* Xen does p2m translation, not guest */
> 
> Please add "and handles refcounts" to the comment describing PG_translate.
> 

Sure.

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