From: "Lan, Tianyu" <tianyu.lan@intel.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: "yang.zhang.wz@gmail.com" <yang.zhang.wz@gmail.com>,
xuquan8@huawei.com, Stefano Stabellini <sstabellini@kernel.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
"ian.jackson@eu.citrix.com" <ian.jackson@eu.citrix.com>,
Kevin Tian <kevin.tian@intel.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
Jun Nakajima <jun.nakajima@intel.com>,
"anthony.perard@citrix.com" <anthony.perard@citrix.com>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: Xen virtual IOMMU high level design doc V2
Date: Wed, 26 Oct 2016 23:03:18 +0800 [thread overview]
Message-ID: <6c0cdcb2-fd77-37d6-9b56-a50a11215b2e@intel.com> (raw)
In-Reply-To: <581095DA0200007800119B0E@prv-mh.provo.novell.com>
On 10/26/2016 5:39 PM, Jan Beulich wrote:
>>>> On 22.10.16 at 09:32, <tianyu.lan@intel.com> wrote:
>> On 10/21/2016 4:36 AM, Andrew Cooper wrote:
>>>>>> 3.5 Implementation consideration
>>>>>> VT-d spec doesn't define a capability bit for the l2 translation.
>>>>>> Architecturally there is no way to tell guest that l2 translation
>>>>>> capability is not available. Linux Intel IOMMU driver thinks l2
>>>>>> translation is always available when VTD exits and fail to be loaded
>>>>>> without l2 translation support even if interrupt remapping and l1
>>>>>> translation are available. So it needs to enable l2 translation first
>>>>>> before other functions.
>>>>>
>>>>> What then is the purpose of the nested translation support bit in the
>>>>> extended capability register?
>>>>
>>>> It's to translate output GPA from first level translation(IOVA->GPA)
>>>> to HPA.
>>>>
>>>> Detail please see VTD spec - 3.8 Nested Translation
>>>> "When Nesting Enable (NESTE) field is 1 in extended-context-entries,
>>>> requests-with-PASID translated through first-level translation are also
>>>> subjected to nested second-level translation. Such extendedcontext-
>>>> entries contain both the pointer to the PASID-table (which contains the
>>>> pointer to the firstlevel translation structures), and the pointer to
>>>> the second-level translation structures."
>>>
>>> I didn't phrase my question very well. I understand what the nested
>>> translation bit means, but I don't understand why we have a problem
>>> signalling the presence or lack of nested translations to the guest.
>>>
>>> In other words, why can't we hide l2 translation from the guest by
>>> simply clearing the nested translation capability?
>>
>> You mean to tell no support of l2 translation via nest translation bit?
>> But the nested translation is a different function with l2 translation
>> even from guest view and nested translation only works requests with
>> PASID (l1 translation).
>>
>> Linux intel iommu driver enables l2 translation unconditionally and free
>> iommu instance when failed to enable l2 translation.
>
> In which cases the wording of your description is confusing: Instead of
> "Linux Intel IOMMU driver thinks l2 translation is always available when
> VTD exits and fail to be loaded without l2 translation support ..." how
> about using something closer to what you've replied with last?
>
Sorry for my pool English. Will update.
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next prev parent reply other threads:[~2016-10-26 15:03 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-26 8:29 Discussion about virtual iommu support for Xen guest Lan Tianyu
2016-05-26 8:42 ` Dong, Eddie
2016-05-27 2:26 ` Lan Tianyu
2016-05-27 8:11 ` Tian, Kevin
2016-05-26 11:35 ` Andrew Cooper
2016-05-27 8:19 ` Lan Tianyu
2016-06-02 15:03 ` Lan, Tianyu
2016-06-02 18:58 ` Andrew Cooper
2016-06-03 11:01 ` Current PVH/HVMlite work and planning (was :Re: Discussion about virtual iommu support for Xen guest) Roger Pau Monne
2016-06-03 11:21 ` Tian, Kevin
2016-06-03 11:52 ` Roger Pau Monne
2016-06-03 12:11 ` Tian, Kevin
2016-06-03 16:56 ` Stefano Stabellini
2016-06-07 5:48 ` Tian, Kevin
2016-06-03 11:17 ` Discussion about virtual iommu support for Xen guest Tian, Kevin
2016-06-03 13:09 ` Lan, Tianyu
2016-06-03 14:00 ` Andrew Cooper
2016-06-03 13:51 ` Andrew Cooper
2016-06-03 14:31 ` Jan Beulich
2016-06-03 17:14 ` Stefano Stabellini
2016-06-07 5:14 ` Tian, Kevin
2016-06-07 7:26 ` Jan Beulich
2016-06-07 10:07 ` Stefano Stabellini
2016-06-08 8:11 ` Tian, Kevin
2016-06-26 13:42 ` Lan, Tianyu
2016-06-29 3:04 ` Tian, Kevin
2016-07-05 13:37 ` Lan, Tianyu
2016-07-05 13:57 ` Jan Beulich
2016-07-05 14:19 ` Lan, Tianyu
2016-08-17 12:05 ` Xen virtual IOMMU high level design doc Lan, Tianyu
2016-08-17 12:42 ` Paul Durrant
2016-08-18 2:57 ` Lan, Tianyu
2016-08-25 11:11 ` Jan Beulich
2016-08-31 8:39 ` Lan Tianyu
2016-08-31 12:02 ` Jan Beulich
2016-09-01 1:26 ` Tian, Kevin
2016-09-01 2:35 ` Lan Tianyu
2016-09-15 14:22 ` Lan, Tianyu
2016-10-05 18:36 ` Konrad Rzeszutek Wilk
2016-10-11 1:52 ` Lan Tianyu
2016-11-23 18:19 ` Edgar E. Iglesias
2016-11-23 19:09 ` Stefano Stabellini
2016-11-24 2:00 ` Tian, Kevin
2016-11-24 4:09 ` Edgar E. Iglesias
2016-11-24 6:49 ` Lan Tianyu
2016-11-24 13:37 ` Edgar E. Iglesias
2016-11-25 2:01 ` Xuquan (Quan Xu)
2016-11-25 5:53 ` Lan, Tianyu
2016-10-18 14:14 ` Xen virtual IOMMU high level design doc V2 Lan Tianyu
2016-10-18 19:17 ` Andrew Cooper
2016-10-20 9:53 ` Tian, Kevin
2016-10-20 18:10 ` Andrew Cooper
2016-10-20 14:17 ` Lan Tianyu
2016-10-20 20:36 ` Andrew Cooper
2016-10-22 7:32 ` Lan, Tianyu
2016-10-26 9:39 ` Jan Beulich
2016-10-26 15:03 ` Lan, Tianyu [this message]
2016-11-03 15:41 ` Lan, Tianyu
2016-10-28 15:36 ` Lan Tianyu
2016-10-18 20:26 ` Konrad Rzeszutek Wilk
2016-10-20 10:11 ` Tian, Kevin
2016-10-20 14:56 ` Lan, Tianyu
2016-10-26 9:36 ` Jan Beulich
2016-10-26 14:53 ` Lan, Tianyu
2016-11-17 15:36 ` Xen virtual IOMMU high level design doc V3 Lan Tianyu
2016-11-18 19:43 ` Julien Grall
2016-11-21 2:21 ` Lan, Tianyu
2016-11-21 13:17 ` Julien Grall
2016-11-21 18:24 ` Stefano Stabellini
2016-11-21 7:05 ` Tian, Kevin
2016-11-23 1:36 ` Lan Tianyu
2016-11-21 13:41 ` Andrew Cooper
2016-11-22 6:02 ` Tian, Kevin
2016-11-22 8:32 ` Lan Tianyu
2016-11-22 10:24 ` Jan Beulich
2016-11-24 2:34 ` Lan Tianyu
2016-06-03 19:51 ` Is: 'basic pci bridge and root device support. 'Was:Re: Discussion about virtual iommu support for Xen guest Konrad Rzeszutek Wilk
2016-06-06 9:55 ` Jan Beulich
2016-06-06 17:25 ` Konrad Rzeszutek Wilk
2016-08-02 15:15 ` Lan, Tianyu
2016-05-27 8:35 ` Tian, Kevin
2016-05-27 8:46 ` Paul Durrant
2016-05-27 9:39 ` Tian, Kevin
2016-05-31 9:43 ` George Dunlap
2016-05-27 2:26 ` Yang Zhang
2016-05-27 8:13 ` Tian, Kevin
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