From: "Jan Beulich" <JBeulich@suse.com>
To: Yu Zhang <yu.c.zhang@linux.intel.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>,
George Dunlap <george.dunlap@citrix.com>,
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: Mon, 20 Jun 2016 07:38:13 -0600 [thread overview]
Message-ID: <57680DE502000078000F6D43@prv-mh.provo.novell.com> (raw)
In-Reply-To: <5767DC60.5010703@linux.intel.com>
>>> On 20.06.16 at 14:06, <yu.c.zhang@linux.intel.com> wrote:
> Suppose resolve_misconfig() is modified to change all p2m_ioreq_server
> entries(which also
> have e.recalc flag turned on) back to p2m_ram_rw. And suppose we have
> ioreq server 1, which
> emulates gfn A, and ioreq server 2 which emulates gfn B:
>
> 1> At the beginning, ioreq server 1 is attached to p2m_ioreq_server, and
> gfn A is write protected
> by setting it to p2m_ioreq_server;
>
> 2> ioreq server 1 is detached from p2m_ioreq_server, left gfn A's p2m
> type unchanged;
>
> 3> After the detachment of ioreq server 1,
> p2m_change_entry_type_global() is called, all ept
> entries are invalidated;
>
> 4> Later, ioreq server 2 is attached to p2m_ioreq_server;
>
> 5> Gfn B is set to p2m_ioreq_server, although its corresponding ept
> entry was invalidated,
> ept_set_entry() will trigger resolve_misconfig(), which will set the p2m
> type of gfn B back to
> p2m_ram_rw;
>
> 6> ept_set_entry() will set gfn B's p2m type to p2m_ioreq_server next;
> And now, we have two
> ept entries with p2m_ioreq_server type - gfn A's and gfn B's.
>
> With no live migration, things could work fine - later accesses to gfn A
> will ultimately change
> its type back to p2m_ram_rw.
>
> However, if live migration is started(all pte entries invalidated
> again), resolve_misconfig() would
> change both gfn A's and gfn B's p2m type back to p2m_ram_rw, which means
> the emulation of
> gfn B would fail.
Why would it? Changes to p2m_ram_logdirty won't alter
p2m_ioreq_server entries, and hence changes from it back to
p2m_ram_rw won't either.
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.
Jan
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next prev parent reply other threads:[~2016-06-20 13:38 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 [this message]
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
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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