Re: [Xen-devel] [PATCH 2/3] xen/p2m: Using INVALID_MFN instead of mfn_valid

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.08.12 at 08:57, Xudong Hao <xudong.hao@xxxxxxxxx> wrote:
> 64 bits big bar's MMIO address may out of the highest gfn, then mfn_valid 
> may return failure, so using INVALID_MFN to measure.

Hmm, that can be true for 32-bit BARs too (on systems with less
than 4Gb).

> Signed-off-by: Xiantao Zhang <xiantao.zhang@xxxxxxxxx>
> Signed-off-by: Xudong Hao <xudong.hao@xxxxxxxxx>
> 
> diff -r 663eb766cdde xen/arch/x86/mm/p2m-ept.c
> --- a/xen/arch/x86/mm/p2m-ept.c       Tue Jul 24 17:02:04 2012 +0200
> +++ b/xen/arch/x86/mm/p2m-ept.c       Thu Jul 26 15:40:01 2012 +0800
> @@ -428,7 +428,7 @@ ept_set_entry(struct p2m_domain *p2m, un
>      }
>  
>      /* Track the highest gfn for which we have ever had a valid mapping */
> -    if ( mfn_valid(mfn_x(mfn)) &&
> +    if ( (mfn_x(mfn) != INVALID_MFN) &&
>           (gfn + (1UL << order) - 1 > p2m->max_mapped_pfn) )
>          p2m->max_mapped_pfn = gfn + (1UL << order) - 1;

Depending on how the above comment gets addressed (i.e.
whether MMIO MFNs are to be considered here at all), this
might need changing anyway, as this a huge max_mapped_pfn
value likely wouldn't be very useful anymore.

Jan



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