Re: [Xen-devel] [PATCH] x86/mm: relax the check in get_pg_owner

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.03.17 at 19:08, <wei.liu2@xxxxxxxxxx> wrote:
> PVH guest is actually an translated guest. It should be able to
> manipulate page table for other domains when acting as Dom0.

The same was true for PVHv1, so I'm afraid there's a little more to
this.

> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -3041,12 +3041,6 @@ static struct domain *get_pg_owner(domid_t domid)
>          goto out;
>      }
>  
> -    if ( unlikely(paging_mode_translate(curr)) )
> -    {
> -        MEM_LOG("Cannot mix foreign mappings with translated domains");
> -        goto out;
> -    }

Prior to Roger's recent removal of PVHv1 code this was

    if ( !is_pvh_domain(curr) && unlikely(paging_mode_translate(curr)) )

Instead of removing the left side, I think it should have been
converted to !is_hvm_domain() (or is_pv_domain()).

Protection against this being used on other than PV domains
as target luckily looks to be there:
- mmuext and mmu_update already have respective (albeit
  somewhat inconsistent) checks,
- do_update_va_mapping_otherdomain() is not wired up for
  HVM.

Jan


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