Re: [Xen-devel] [PATCH 2/2] x86: add pte_set_flags/clear_flags forpteflag manipulation

[Jeremy Fitzhardinge]

Jan Beulich wrote:
> Whether a pte is live doesn't matter here: If you change P on Xen, the
> frame number representation *must* change from/to PFN to/from MFN.
> In no case (other than iomem pages) is it allowed to flip just this bit.

Yes, true. Same with _PAGE_SPECIAL, which is actually flipped by code 
here.  I guess a warning here might be useful, but really the calling 
code needs to be properly disciplined; after all setting P on a swap 
entry is no fun either.

   J
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