Re: [Xen-devel] [v3][PATCH 00/16] Fix RMRR

[Tim Deegan <tim@xxxxxxx>]

Hi,

At 09:15 +0800 on 11 Jun (1434014109), Tiejun Chen wrote:
> * Two changes for runtime cycle
>    patch #2,xen/x86/p2m: introduce set_identity_p2m_entry, on hypervisor side
> 
>   a>. Introduce paging_mode_translate()
>   Otherwise, we'll see this error when boot Xen/Dom0

Righto.  Looking at the patch, it would be neater to have

    if ( !paging_mode_translate(p2m->domain) )
        return 0;

at the start, instead of indenting the whole body of the function in
an inner scope.

>   b>. Actually we still need to use "mfn_x(mfn) == INVALID_MFN" to confirm
>   we're getting an invalid mfn.

Can you give a concrete example of when this is needed?  The code now
looks like this: 

       if ( p2mt == p2m_invalid || mfn_x(mfn) == INVALID_MFN )
           ret = p2m_set_entry(p2m, gfn, _mfn(gfn), PAGE_ORDER_4K,
                               p2m_mmio_direct, p2ma);

which will catch any invalid-mfn mapping, including paged-out pages
&c.   I suspect the case you care about is the default p2m_mmio_dm type,
which would be better handeld explicitly:

       if ( p2mt == p2m_invalid || p2mt == p2m_mmio_dm )
           ...

Cheers,

Tim.

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