From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH v3 04/16] hypervisor part of add vmware_port
	to xl.cfg
Date: Mon, 8 Sep 2014 16:32:02 +0100
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To: Jan Beulich <JBeulich@suse.com>, xen-devel@lists.xen.org, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Don Slutz <dslutz@verizon.com>
Cc: Kevin Tian <kevin.tian@intel.com>, Keir Fraser <keir@xen.org>, Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Jun Nakajima <jun.nakajima@intel.com>, Eddie Dong <eddie.dong@intel.com>, Ian Jackson <ian.jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>, Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>, Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
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On 08/09/14 16:22, Jan Beulich wrote:
>>>> On 08.09.14 at 17:01, <boris.ostrovsky@oracle.com> wrote:
>> I wonder whether we should enable #GP intercepts only when we know that 
>> the guest is VMware-aware (which we do as far as I can tell since we 
>> have a config option).
> I didn't look at the patches themselves yes, but I very much expected
> this to now be the case considering discussion on the earlier version.
> If it's not, I'm not even sure looking at the new version is going to be
> of much use...
>
> Jan
>

I find it incredibly hard to believe that VMWare do unconditional #GP
exits, and looking at the Intel manual, you do not actually need to
intercept #GP faults.

The "unconditional I/O exiting" control can be used to cherry-pick
specific IO ports in combination with the IO port bitmap, ahead of the
#GP fault due to a failure of IOPL.  I would expect AMD has a similar
option.

~Andrew