Re: [Xen-devel] [V9 PATCH 6/8] pvh dom0: Add and remove foreign pages

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 26.04.14 at 03:34, <mukesh.rathor@xxxxxxxxxx> wrote:
> Ok, so far:
> 
> option 1, Jan's suggestion: 
>   - Use my latest patch, but add explicit set of p2m type for intermediate
>     entries in ept_set_middle_entry() like Jan said.
> 
>     Good: we won't need to then worry about checking for leaf entries.
>     Bad: future code can't use the bits for interm entries.
> 
> option 2, Tim's suggestion:
>   - Use my latest patch, but add sp = 1 in leaf entries. Then use level
>     to figure if we are in superpage. Will work too, but will change the
>     definition of sp bit, and superpage check will always require checking
>     for level. 
> 
> option 3:
>   - Pass level to atomic_write_ept_entry() and check for foreign only in
>     case of level == 0, ie leaf entries where foreign can be set.
> 
>     It appears that information is available at all call sites, and would
>     be least intrusive in terms of using bits for non-leaf entries.
> 
> option 4:
>   - each call site checks for level and calls either macro for leaf entry
>     or macro for non-leaf entry. same as 3, but the check is in call site.

I think my preference would go backwards from 4 to 1, but I think
Tim would - like you - prefer 3 over 4, which I wouldn't object to.

Jan


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