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Re: [Xen-devel] [PATCH] [HVM] Patches to make HVM capable of running OS/2.

On 16/3/07 12:45, "Trolle Selander" <trolle.selander@xxxxxxxxx> wrote:

I thought they were marked as reserved in the e820 map right now, but now that I checked, you're right that they're not mentioned, which means they're actually nearly as "unprotected" from a modern OS as from a pre-e820-aware one like OS/2. Nasty.
In any case, I still don't see why the ioreq and buffered io pages should be inside the guest's memory space at all. What's the issue with keeping them completely outside the guest's visible RAM and only shared between HV & Dom0?

If the pages belong to the domU then they have to be part of its pseudophysical address space, otherwise dom0 cannot map them (since HVM pages are always mapped by pfn, not by mfn).

We could make the pages belong to dom0, or to Xen, I suppose, but that’s not the road we’ve gone down and there’s not really any reason to change now. We should just keep the pages out of the guest’s way so he doesn’t accidentally use them as RAM or map on top of them!

 -- Keir
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