From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Vrabel <david.vrabel@citrix.com>
Subject: Re: Xen PV PTE ABI (or lack thereof)
Date: Thu, 21 Jan 2016 14:53:38 +0000
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To: Andrew Cooper <andrew.cooper3@citrix.com>, David Vrabel <david.vrabel@citrix.com>, Jan Beulich <JBeulich@suse.com>
Cc: George Dunlap <george.dunlap@eu.citrix.com>, Huaitong Han <huaitong.han@intel.com>, Tim Deegan <tim@xen.org>, Xen-devel List <xen-devel@lists.xen.org>
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On 21/01/16 14:37, Andrew Cooper wrote:

>> I think we should document the PV ABI as-is. i.e., that these two PTE
>> bits are not available for PV guest use.
> 
> This is already known to break some guests.  It shouldn't stay as it
> currently is.

It's unfortunate that the current ABI is incompatible with some guests
in some situations, but it can't be fixed without adding a mechanism for
the guest to query or negotiate PTE bit availability since existing
guests have to be able to run on older hypervisors.

David