From: George Dunlap <george.dunlap@citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Lan Tianyu <tianyu.lan@intel.com>,
yang.zhang.wz@gmail.com, "Tian, Kevin" <kevin.tian@intel.com>,
Stefano Stabellini <sstabellini@kernel.org>,
"Nakajima, Jun" <jun.nakajima@intel.com>,
"Dong, Eddie" <eddie.dong@intel.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
Jan Beulich <jbeulich@suse.com>,
Anthony Perard <anthony.perard@citrix.com>
Subject: Re: Discussion about virtual iommu support for Xen guest
Date: Tue, 31 May 2016 10:43:18 +0100 [thread overview]
Message-ID: <CAFLBxZZoFkMJjkMzH8_CLC3aDatMfip7fTb3R0iSBNhJWcQrBA@mail.gmail.com> (raw)
In-Reply-To: <5746DF93.8090803@citrix.com>
On Thu, May 26, 2016 at 12:35 PM, Andrew Cooper
<andrew.cooper3@citrix.com> wrote:
> On 26/05/16 09:29, Lan Tianyu wrote:
>> Hi All:
>> We try pushing virtual iommu support for Xen guest and there are some
>> features blocked by it.
>>
>> Motivation:
>> -----------------------
>> 1) Add SVM(Shared Virtual Memory) support for Xen guest
>> To support iGFX pass-through for SVM enabled devices, it requires
>> virtual iommu support to emulate related registers and intercept/handle
>> guest SVM configure in the VMM.
>>
>> 2) Increase max vcpu support for one VM.
>>
>> So far, max vcpu for Xen hvm guest is 128. For HPC(High Performance
>> Computing) cloud computing, it requires more vcpus support in a single
>> VM. The usage model is to create just one VM on a machine with the
>> same number vcpus as logical cpus on the host and pin vcpu on each
>> logical cpu in order to get good compute performance.
>>
>> Intel Xeon phi KNL(Knights Landing) is dedicated to HPC market and
>> supports 288 logical cpus. So we hope VM can support 288 vcpu
>> to meet HPC requirement.
>>
>> Current Linux kernel requires IR(interrupt remapping) when MAX APIC
>> ID is > 255 because interrupt only can be delivered among 0~255 cpus
>> without IR. IR in VM relies on the virtual iommu support.
>>
>> KVM Virtual iommu support status
>> ------------------------
>> Current, Qemu has a basic virtual iommu to do address translation for
>> virtual device and it only works for the Q35 machine type. KVM reuses it
>> and Redhat is adding IR to support more than 255 vcpus.
>>
>> How to add virtual iommu for Xen?
>> -------------------------
>> First idea came to my mind is to reuse Qemu virtual iommu but Xen didn't
>> support Q35 so far. Enabling Q35 for Xen seems not a short term task.
>> Anthony did some related jobs before.
>>
>> I'd like to see your comments about how to implement virtual iommu for Xen.
>>
>> 1) Reuse Qemu virtual iommu or write a separate one for Xen?
>> 2) Enable Q35 for Xen to reuse Qemu virtual iommu?
>>
>> Your comments are very appreciated. Thanks a lot.
>
> To be viable going forwards, any solution must work with PVH/HVMLite as
> much as HVM. This alone negates qemu as a viable option.
There's a big difference between "suboptimal" and "not viable".
Obviously it would be nice to be able to have HVMLite do graphics
pass-through, but if this functionality ends up being HVM-only, is
that really such a huge issue?
If as Paul seems to indicate, the extra work to get the functionality
in Xen isn't very large, then it's worth pursuing; but I don't think
we should take other options off the table.
-George
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next prev parent reply other threads:[~2016-05-31 9:43 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
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 [this message]
2016-05-27 2:26 ` Yang Zhang
2016-05-27 8:13 ` Tian, Kevin
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