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Re: [Xen-devel] [v5][PATCH 1/2] xen:x86:mm:p2m: introduce set_identity_p2m_entry

On 2014/7/29 17:53, Jan Beulich wrote:
On 29.07.14 at 11:11, <tiejun.chen@xxxxxxxxx> wrote:
On 2014/7/29 16:19, Jan Beulich wrote:
? Of course it may still be necessary to also inspect the obtained p2mt
and a.

Are you saying this?

        if ( !p2m_is_valid(p2mt) ||
             !mfn_valid(mfn) ||
             (a != p2m_access_rw) )

I'm afraid that's not enough context to know whether what you
mean to do is sufficient. Plus !p2m_is_valid() is too weak. You
simply need to properly think through what should happen if you
find a valid mapping, but any of the tuple (mfn, p2mt, a) don't
match what you intend to be there.

Actually as I understand we can create these mapping only in one case of !mfn_valid(mfn). For others scenarios we just return with that warning message no matter what that tuple is explicitly. So here I try to understand why you're saying we need check more by show this condition combination.


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