Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality

From	Boris Ostrovsky <boris.ostrovsky@oracle.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality
Date	2017-09-12 18:30 +0200
Message-ID	<uoWet-3Az-3@gated-at.bofh.it> (permalink)
References	(1 earlier) <unu0W-Sv-15@gated-at.bofh.it> <uoVBN-37Z-55@gated-at.bofh.it> <uoVLs-3bm-5@gated-at.bofh.it> <uoVV8-3tT-25@gated-at.bofh.it> <uoVV8-3tT-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On 09/12/2017 12:09 PM, Juergen Gross wrote:
> On 12/09/17 18:05, Boris Ostrovsky wrote:
>> On 09/12/2017 11:50 AM, Juergen Gross wrote:
>>> On 12/09/17 17:44, Boris Ostrovsky wrote:
>>>> On 09/08/2017 10:48 AM, Juergen Gross wrote:
>>>>> As there is currently no user for sub-page grants or transient grants
>>>>> remove that functionality. This at once makes it possible to switch
>>>>> from grant v2 to grant v1 without restrictions, as there is no loss of
>>>>> functionality other than the limited frame number width related to
>>>>> the switch.
>>>> But isn't that ABI violation? v2 is expected to support this (XSAs
>>>> notwithstanding)
>>> No, I don't think so.
>>>
>>> The hypervisor still supports it, but the domU (or dom0) isn't required
>>> to make use of all the features IMHO. Or are you aware of any backend
>>> querying the grant version of a frontend and acting in another way if v2
>>> is detected?
>> I am not aware of any but that doesn't mean that they don't (or won't)
>> exist.
> But isn't the frontend the one which is defining what is granted in
> which way? How should there be an ABI breakage when the frontend just
> isn't using sub-page or transitive grants?

People may provide both front and backend drivers and frontends, knowing
that v2 is available, could decide to use those features.

-boris

Thread

Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-09-12 17:50 +0200
  Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Juergen Gross <jgross@suse.com> - 2017-09-12 18:00 +0200
    Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Juergen Gross <jgross@suse.com> - 2017-09-12 18:10 +0200
      Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-09-12 18:30 +0200
        Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Juergen Gross <jgross@suse.com> - 2017-09-12 20:20 +0200
          Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-09-13 15:30 +0200
            Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Juergen Gross <jgross@suse.com> - 2017-09-13 15:40 +0200
              Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-09-13 16:00 +0200
                Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Juergen Gross <jgross@suse.com> - 2017-09-13 16:50 +0200
                Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-09-13 18:30 +0200
                Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Juergen Gross <jgross@suse.com> - 2017-09-14 10:20 +0200
    Re: [PATCH 2/4] xen: limit grant v2 interface to the v1 functionality Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-09-12 18:10 +0200

csiph-web