Subject: Re: [Xen-devel] [PATCH 6/8] xen/pvh: Initialize grant table for PVH
 guests
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
References: <1476468318-24422-1-git-send-email-boris.ostrovsky@oracle.com>
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 <20161014191923.GD16777@localhost.localdomain>
 <d04cd053-c452-e8ef-c111-64b4bdb5aa3b@oracle.com>
 <20161014195134.GA22782@char.us.oracle.com>
Cc: david.vrabel@citrix.com, JGross@suse.com,
        xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
        roger.pau@citrix.com
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Message-ID: <e4ca517d-aa29-68d4-c23a-bab1ca4bf662@oracle.com>
Date: Fri, 14 Oct 2016 16:02:52 -0400
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On 10/14/2016 03:51 PM, Konrad Rzeszutek Wilk wrote:
> On Fri, Oct 14, 2016 at 03:43:19PM -0400, Boris Ostrovsky wrote:
>> On 10/14/2016 03:19 PM, Konrad Rzeszutek Wilk wrote:
>>> On Fri, Oct 14, 2016 at 02:05:16PM -0400, Boris Ostrovsky wrote:
>>>
>>> Perhaps add in here:
>>>
>>> PVH is like PV in that there are no PCI devices - which HVM
>>> code would piggyback on to find the Xen PCI platform device and
>>> use its MMIO space to stash the grants in.
>>>
>>> For PVH we balloon out memory and stash the grants in there.
>>>
>>> (Which begs the next question - where and when do we balloon out the
>>> normal memory back in?)
>> Are you saying that we should get back memory that we gave to grant tables?
> Yes.
>
> In pure HVM that area is MMIO - which hvmloader has balloonned out.
>
> The hvmloader then balloons that number of pages back  at the end of
> guest memory (after 4GB).

We don't do this for PV though, do we?

-boris