From: Yu Zhang <yu.c.zhang@linux.intel.com>
To: Jan Beulich <JBeulich@suse.com>,
George Dunlap <george.dunlap@citrix.com>
Cc: Kevin Tian <kevin.tian@intel.com>,
George Dunlap <george.dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Tim Deegan <tim@xen.org>,
xen-devel@lists.xen.org, Paul Durrant <paul.durrant@citrix.com>,
zhiyuan.lv@intel.com, JunNakajima <jun.nakajima@intel.com>
Subject: Re: [PATCH v4 3/3] x86/ioreq server: Add HVMOP to map guest ram with p2m_ioreq_server to an ioreq server.
Date: Wed, 22 Jun 2016 16:38:56 +0800 [thread overview]
Message-ID: <576A4EA0.9020403@linux.intel.com> (raw)
In-Reply-To: <576A4ED702000078000F7733@prv-mh.provo.novell.com>
On 6/22/2016 2:39 PM, Jan Beulich wrote:
>>>> On 21.06.16 at 16:38, <george.dunlap@citrix.com> wrote:
>> On 21/06/16 10:47, Jan Beulich wrote:
>>>>>>> And then - didn't we mean to disable that part of XenGT during
>>>>>>> migration, i.e. temporarily accept the higher performance
>>>>>>> overhead without the p2m_ioreq_server entries? In which case
>>>>>>> flipping everything back to p2m_ram_rw after (completed or
>>>>>>> canceled) migration would be exactly what we want. The (new
>>>>>>> or previous) ioreq server should attach only afterwards, and
>>>>>>> can then freely re-establish any p2m_ioreq_server entries it
>>>>>>> deems necessary.
>>>>>>>
>>>>>> Well, I agree this part of XenGT should be disabled during migration.
>>>>>> But in such
>>>>>> case I think it's device model's job to trigger the p2m type
>>>>>> flipping(i.e. by calling
>>>>>> HVMOP_set_mem_type).
>>>>> I agree - this would seem to be the simpler model here, despite (as
>>>>> George validly says) the more consistent model would be for the
>>>>> hypervisor to do the cleanup. Such cleanup would imo be reasonable
>>>>> only if there was an easy way for the hypervisor to enumerate all
>>>>> p2m_ioreq_server pages.
>>>> Well, for me, the "easy way" means we should avoid traversing the whole ept
>>>> paging structure all at once, right?
>>> Yes.
>> Does calling p2m_change_entry_type_global() not satisfy this requirement?
> Not really - that addresses the "low overhead" aspect, but not the
> "enumerate all such entries" one.
>
>>>> I have not figured out any clean
>>>> solution
>>>> in hypervisor side, that's one reason I'd like to left this job to
>>>> device model
>>>> side(another reason is that I do think device model should take this
>>>> responsibility).
>>> Let's see if we can get George to agree.
>> Well I had in principle already agreed to letting this be the interface
>> on the previous round of patches; we're having this discussion because
>> you (Jan) asked about what happens if an ioreq server is de-registered
>> while there are still outstanding p2m types. :-)
> Indeed. Yet so far I understood you didn't like de-registration to
> both not do the cleanup itself and fail if there are outstanding
> entries.
>
>> I do think having Xen change the type makes the most sense, but if
>> you're happy to leave that up to the ioreq server, I'm OK with things
>> being done that way as well. I think we can probably change it later if
>> we want.
> Yes, since ioreq server interfaces will all be unstable ones, that
> shouldn't be a problem. Albeit that's only the theory. With the call
> coming from the device model, we'd need to make sure to put all
> the logic (if any) to deal with the hypervisor implementation details
> into libxc, so the caller of the libxc interface won't need to change.
> I've learned during putting together the hvmctl series that this
> wasn't done cleanly enough for one of the existing interfaces (see
> patch 10 of that series).
Thanks Jan & George. So I guess you both accepted that we can left the
clean up to
the device model side, right?
B.R.
Yu
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next prev parent reply other threads:[~2016-06-22 8:38 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-19 9:05 [PATCH v4 0/3] x86/ioreq server: Introduce HVMMEM_ioreq_server mem type Yu Zhang
2016-05-19 9:05 ` [PATCH v4 1/3] x86/ioreq server: Rename p2m_mmio_write_dm to p2m_ioreq_server Yu Zhang
2016-06-14 10:04 ` Jan Beulich
2016-06-14 13:14 ` George Dunlap
2016-06-15 10:51 ` Yu Zhang
2016-05-19 9:05 ` [PATCH v4 2/3] x86/ioreq server: Add new functions to get/set memory types Yu Zhang
2016-05-19 9:05 ` [PATCH v4 3/3] x86/ioreq server: Add HVMOP to map guest ram with p2m_ioreq_server to an ioreq server Yu Zhang
2016-06-14 10:45 ` Jan Beulich
2016-06-14 13:13 ` George Dunlap
2016-06-14 13:31 ` Jan Beulich
2016-06-15 9:50 ` George Dunlap
2016-06-15 10:21 ` Jan Beulich
2016-06-15 11:28 ` George Dunlap
2016-06-16 9:30 ` Yu Zhang
2016-06-16 9:55 ` Jan Beulich
2016-06-17 10:17 ` George Dunlap
2016-06-20 9:03 ` Yu Zhang
2016-06-20 10:10 ` George Dunlap
2016-06-20 10:25 ` Jan Beulich
2016-06-20 10:32 ` George Dunlap
2016-06-20 10:55 ` Jan Beulich
2016-06-20 11:28 ` Yu Zhang
2016-06-20 13:13 ` George Dunlap
2016-06-21 7:42 ` Yu Zhang
2016-06-20 10:30 ` Yu Zhang
2016-06-20 10:43 ` George Dunlap
2016-06-20 10:45 ` Jan Beulich
2016-06-20 11:06 ` Yu Zhang
2016-06-20 11:20 ` Jan Beulich
2016-06-20 12:06 ` Yu Zhang
2016-06-20 13:38 ` Jan Beulich
2016-06-21 7:45 ` Yu Zhang
2016-06-21 8:22 ` Jan Beulich
2016-06-21 9:16 ` Yu Zhang
2016-06-21 9:47 ` Jan Beulich
2016-06-21 10:00 ` Yu Zhang
2016-06-21 14:38 ` George Dunlap
2016-06-22 6:39 ` Jan Beulich
2016-06-22 8:38 ` Yu Zhang [this message]
2016-06-22 9:11 ` Jan Beulich
2016-06-22 9:16 ` George Dunlap
2016-06-22 9:29 ` Jan Beulich
2016-06-22 9:47 ` George Dunlap
2016-06-22 10:07 ` Yu Zhang
2016-06-22 11:33 ` George Dunlap
2016-06-23 7:37 ` Yu Zhang
2016-06-23 10:33 ` George Dunlap
2016-06-24 4:16 ` Yu Zhang
2016-06-24 6:12 ` Jan Beulich
2016-06-24 7:12 ` Yu Zhang
2016-06-24 8:01 ` Jan Beulich
2016-06-24 9:57 ` Yu Zhang
2016-06-24 10:27 ` Jan Beulich
2016-06-22 10:10 ` Jan Beulich
2016-06-22 10:15 ` George Dunlap
2016-06-22 11:50 ` Jan Beulich
2016-06-15 10:52 ` Yu Zhang
2016-06-15 12:26 ` Jan Beulich
2016-06-16 9:32 ` Yu Zhang
2016-06-16 10:02 ` Jan Beulich
2016-06-16 11:18 ` Yu Zhang
2016-06-16 12:43 ` Jan Beulich
2016-06-20 9:05 ` Yu Zhang
2016-06-14 13:14 ` George Dunlap
2016-05-27 7:52 ` [PATCH v4 0/3] x86/ioreq server: Introduce HVMMEM_ioreq_server mem type Zhang, Yu C
2016-05-27 10:00 ` Jan Beulich
2016-05-27 9:51 ` Zhang, Yu C
2016-05-27 10:02 ` George Dunlap
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