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From: Alex Williamson <alex.williamson@redhat.com>
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Subject: Re: [Qemu-devel] =?utf-8?q?About_virtio_device_hotplug_in_Q35!_?=
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To: Bob Chen <a175818323@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel@redhat.com>, =?UTF-8?B?6ZmI5Y2a?= <chenbo02@meituan.com>, qemu-devel@nongnu.org

On Tue, 8 Aug 2017 09:44:56 +0800
Bob Chen <a175818323@gmail.com> wrote:

> 1. How to test the KVM exit rate?

You can use tracing: http://www.linux-kvm.org/page/Tracing
 
> 2. The switches are separate devices of PLX Technology
> 
> # lspci -s 07:08.0 -nn
> 07:08.0 PCI bridge [0604]: PLX Technology, Inc. PEX 8747 48-Lane, 5-Port
> PCI Express Gen 3 (8.0 GT/s) Switch [10b5:8747] (rev ca)
> 
> # This is one of the Root Ports in the system.
> [0000:00]-+-00.0  Intel Corporation Xeon E7 v4/Xeon E5 v4/Xeon E3 v4/Xeon D
> DMI2
>              +-01.0-[01]----00.0  LSI Logic / Symbios Logic MegaRAID SAS
> 2208 [Thunderbolt]
>              +-02.0-[02-05]--
>              +-03.0-[06-09]----00.0-[07-09]--+-08.0-[08]--+-00.0  NVIDIA
> Corporation GP102 [TITAN Xp]
>              |                               |            \-00.1  NVIDIA
> Corporation GP102 HDMI Audio Controller
>              |                               \-10.0-[09]--+-00.0  NVIDIA
> Corporation GP102 [TITAN Xp]
>              |                                            \-00.1  NVIDIA
> Corporation GP102 HDMI Audio Controller
> 
> 
> 
> 
> 3. ACS
> 
> It seemed that I had misunderstood your point? I finally found ACS
> information on switches, not on GPUs.
> 
> Capabilities: [f24 v1] Access Control Services
> ACSCap: SrcValid+ TransBlk+ ReqRedir+ CmpltRedir+ UpstreamFwd+ EgressCtrl+
> DirectTrans+
> ACSCtl: SrcValid+ TransBlk- ReqRedir+ CmpltRedir+ UpstreamFwd+ EgressCtrl-
> DirectTrans-

Yes, NVIDIA uses the same PLX PEX 8747 on the switches on the cards I
have access to.  Unfortunately the endpoints in my case do not support
ATS, so the endpoint cannot generate a pre-translated address that
would take advantage of the DT capability on the switch port if we were
to enable it.  Thanks,

Alex