From: "Yu, Zhang" <yu.c.zhang@linux.intel.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: kevin.tian@intel.com, wei.liu2@citrix.com,
ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com,
andrew.cooper3@citrix.com,
Ian Jackson <Ian.Jackson@eu.citrix.com>,
xen-devel@lists.xen.org, Paul.Durrant@citrix.com,
zhiyuan.lv@intel.com, keir@xen.org
Subject: Re: [PATCH v3 3/3] tools: introduce parameter max_wp_ram_ranges.
Date: Tue, 2 Feb 2016 23:00:21 +0800 [thread overview]
Message-ID: <56B0C485.8070206@linux.intel.com> (raw)
In-Reply-To: <56B0CE8102000078000CD8D4@prv-mh.provo.novell.com>
On 2/2/2016 10:42 PM, Jan Beulich wrote:
>>>> On 02.02.16 at 15:01, <yu.c.zhang@linux.intel.com> wrote:
>> On 2/2/2016 7:12 PM, Jan Beulich wrote:
>>>>>> On 02.02.16 at 11:56, <yu.c.zhang@linux.intel.com> wrote:
>>>> I understand your concern, and to be honest, I do not think
>>>> this is an optimal solution. But I also have no better idea
>>>> in mind. :(
>>>> Another option may be: instead of opening this parameter to
>>>> the tool stack, we use a XenGT flag, which set the rangeset
>>>> limit to a default value. But like I said, this default value
>>>> may not always work on future XenGT platforms.
>>>
>>> Assuming that you think of something set e.g. by hypervisor
>>> command line option: How would that work? I.e. how would
>>> that limit the resource use for all VMs not using XenGT? Or if
>>> you mean a flag settable in the domain config - how would you
>>> avoid a malicious admin to set this flag for all the VMs created
>>> in the controlled partition of the system?
>>
>> Well, I am not satisfied with this new parameter, because:
>> 1> exposing an option like max_wp_ram_ranges to the user seems too
>> detailed;
>> 2> but if not, using a XenGT flag means it would be hard for hypervisor
>> to find a default value which can work in all situations theoretically,
>> although in practice, 8K is already a big enough one.
>>
>> However, as to the security concern you raised, I can not fully
>> understand. :) E.g. I believe a malicious admin can also breach the
>> system even without this patch. This argument may not be convincing to
>> you, but as to this specific case, even if an admin set XenGT flag to
>> all VMs, what harm will this action do? It only means the ioreq server
>> can at most allocate 8K ranges, will that consume all the Xen heaps,
>> especially for 64 bit Xen?
>
> First of all so far you meant to set a limit of 4G, which - taking a
> handful of domains - if fully used would take even a mid-size
> host out of memory. And then you have to consider bad effects
> resulting from Xen itself not normally having a lot of memory left
> (especially when "dom0_mem=" is not forcing most of the memory
> to be in Xen's hands), which may mean that one domain
> exhausting Xen's memory can affect another domain if Xen can't
> allocate memory it needs to support that other domain, in the
> worst case leading to a domain crash. And this all is still leaving
> aside Xen's own health...
>
Thanks, Jan.
The limit of 4G is to avoid the data missing from uint64 to uint32
assignment. And I can accept the 8K limit for XenGT in practice.
After all, it is vGPU page tables we are trying to trap and emulate,
not normal page frames.
And I guess the reason that one domain exhausting Xen's memory can
affect another domain is because rangeset uses Xen heap, instead of the
per-domain memory. So what about we use a 8K limit by now for XenGT,
and in the future, if a per-domain memory allocation solution for
rangeset is ready, we do need to limit the rangeset size. Does this
sounds more acceptable?
B.R.
Yu
next prev parent reply other threads:[~2016-02-02 15:00 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-29 10:45 [PATCH v12 0/3] Refactor ioreq server for better performance Yu Zhang
2016-01-29 10:45 ` [PATCH v12 1/3] Refactor rangeset structure " Yu Zhang
2016-01-29 10:45 ` [PATCH v12 2/3] Differentiate IO/mem resources tracked by ioreq server Yu Zhang
2016-01-29 10:45 ` [PATCH v3 3/3] tools: introduce parameter max_wp_ram_ranges Yu Zhang
2016-01-29 16:33 ` Jan Beulich
2016-01-30 14:38 ` Yu, Zhang
2016-02-01 7:52 ` Jan Beulich
2016-02-01 12:02 ` Wei Liu
2016-02-01 12:15 ` Jan Beulich
2016-02-01 12:49 ` Wei Liu
2016-02-01 13:07 ` Jan Beulich
2016-02-01 15:14 ` Yu, Zhang
2016-02-01 16:16 ` Jan Beulich
2016-02-01 16:33 ` Yu, Zhang
2016-02-01 16:19 ` Yu, Zhang
2016-02-01 16:35 ` Jan Beulich
2016-02-01 16:37 ` Yu, Zhang
2016-02-01 17:05 ` Ian Jackson
2016-02-02 8:04 ` Yu, Zhang
2016-02-02 11:51 ` Wei Liu
2016-02-02 13:56 ` Yu, Zhang
2016-02-02 10:32 ` Jan Beulich
2016-02-02 10:56 ` Yu, Zhang
2016-02-02 11:12 ` Jan Beulich
2016-02-02 14:01 ` Yu, Zhang
2016-02-02 14:42 ` Jan Beulich
2016-02-02 15:00 ` Yu, Zhang [this message]
2016-02-02 15:21 ` Jan Beulich
2016-02-02 15:19 ` Yu, Zhang
2016-02-03 7:10 ` Yu, Zhang
2016-02-03 8:32 ` Jan Beulich
2016-02-03 12:20 ` Paul Durrant
2016-02-03 12:35 ` Jan Beulich
2016-02-03 12:50 ` Paul Durrant
2016-02-03 13:00 ` Jan Beulich
2016-02-03 13:07 ` Paul Durrant
2016-02-03 13:17 ` Jan Beulich
2016-02-03 13:18 ` Paul Durrant
2016-02-03 14:43 ` Ian Jackson
2016-02-03 15:10 ` Paul Durrant
2016-02-03 17:50 ` George Dunlap
2016-02-04 8:50 ` Yu, Zhang
2016-02-03 17:41 ` George Dunlap
2016-02-03 18:21 ` George Dunlap
2016-02-03 18:26 ` George Dunlap
2016-02-03 18:39 ` Andrew Cooper
2016-02-03 19:12 ` George Dunlap
2016-02-04 8:51 ` Yu, Zhang
2016-02-04 10:49 ` George Dunlap
2016-02-04 11:08 ` Ian Campbell
2016-02-04 11:19 ` Ian Campbell
2016-02-04 8:50 ` Yu, Zhang
2016-02-04 9:28 ` Paul Durrant
2016-02-04 9:38 ` Yu, Zhang
2016-02-04 9:49 ` Paul Durrant
2016-02-04 10:34 ` Jan Beulich
2016-02-04 13:33 ` Ian Jackson
2016-02-04 13:47 ` Paul Durrant
2016-02-04 14:12 ` Jan Beulich
2016-02-04 14:25 ` Paul Durrant
2016-02-04 15:06 ` Ian Jackson
2016-02-04 15:51 ` Paul Durrant
2016-02-05 3:47 ` Tian, Kevin
2016-02-05 3:35 ` Tian, Kevin
2016-02-04 14:08 ` Jan Beulich
2016-02-04 17:12 ` George Dunlap
2016-02-05 4:18 ` Tian, Kevin
2016-02-05 8:41 ` Yu, Zhang
2016-02-05 8:32 ` Jan Beulich
2016-02-05 9:24 ` Paul Durrant
2016-02-05 10:41 ` Jan Beulich
2016-02-05 11:14 ` George Dunlap
2016-02-05 11:24 ` Paul Durrant
2016-02-16 7:22 ` Tian, Kevin
2016-02-16 8:50 ` Paul Durrant
2016-02-16 10:33 ` Jan Beulich
2016-02-16 11:11 ` Paul Durrant
2016-02-17 3:18 ` Tian, Kevin
2016-02-17 8:58 ` Paul Durrant
2016-02-17 9:32 ` Jan Beulich
2016-02-17 9:58 ` Tian, Kevin
2016-02-17 10:03 ` Paul Durrant
2016-02-17 10:22 ` Jan Beulich
2016-02-17 10:24 ` Paul Durrant
2016-02-17 10:25 ` Tian, Kevin
2016-02-17 11:01 ` George Dunlap
2016-02-17 11:12 ` Paul Durrant
2016-02-22 15:56 ` George Dunlap
2016-02-22 16:02 ` Paul Durrant
2016-02-22 16:45 ` George Dunlap
2016-02-22 17:01 ` Paul Durrant
2016-02-22 17:23 ` George Dunlap
2016-02-22 17:34 ` Paul Durrant
2016-02-05 8:41 ` Yu, Zhang
2016-02-04 11:06 ` George Dunlap
2016-02-05 2:01 ` Zhiyuan Lv
2016-02-05 3:44 ` Tian, Kevin
2016-02-05 8:38 ` Jan Beulich
2016-02-05 11:05 ` George Dunlap
2016-02-05 15:13 ` Zhiyuan Lv
2016-02-05 20:14 ` George Dunlap
2016-02-05 8:40 ` Yu, Zhang
2016-02-04 10:06 ` Ian Campbell
2016-02-05 3:31 ` Tian, Kevin
2016-02-02 11:31 ` Andrew Cooper
2016-02-02 11:43 ` Jan Beulich
2016-02-02 14:20 ` Andrew Cooper
2016-02-01 11:57 ` Wei Liu
2016-02-01 15:15 ` Yu, Zhang
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