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From: Bob Chen <a175818323@gmail.com>
Date: Wed, 30 Aug 2017 17:41:20 +0800
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Subject: Re: [Qemu-devel] =?utf-8?q?About_virtio_device_hotplug_in_Q35!_?=
	=?utf-8?b?44CQ5aSW5Z+f6YKu5Lu2LuiwqOaFjuafpemYheOAkQ==?=
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To: Alex Williamson <alex.williamson@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel@redhat.com>, =?UTF-8?B?6ZmI5Y2a?= <chenbo02@meituan.com>, qemu-devel@nongnu.org

I think I have observed what you said...

The link speed on host remained 8GT/s until I finished running
p2pBandwidthLatencyTest
for the first time. Then it became 2.5GT/s...


# lspci -s 09:00.0 -vvv
09:00.0 3D controller: NVIDIA Corporation GM204GL [Tesla M60] (rev a1)
Subsystem: NVIDIA Corporation Device 115e
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr+
Stepping- SERR+ FastB2B- DisINTx-
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort-
<MAbort- >SERR- <PERR- INTx-
Latency: 0, Cache Line Size: 32 bytes
Interrupt: pin A routed to IRQ 7
NUMA node: 0
Region 0: Memory at 92000000 (32-bit, non-prefetchable) [size=16M]
Region 1: Memory at 3b800000000 (64-bit, prefetchable) [size=8G]
Region 3: Memory at 3ba00000000 (64-bit, prefetchable) [size=32M]
Capabilities: [60] Power Management version 3
Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
Capabilities: [68] MSI: Enable- Count=1/1 Maskable- 64bit+
Address: 0000000000000000  Data: 0000
Capabilities: [78] Express (v2) Endpoint, MSI 00
DevCap: MaxPayload 256 bytes, PhantFunc 0, Latency L0s unlimited, L1 <64us
ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset- SlotPowerLimit 25.000W
DevCtl: Report errors: Correctable+ Non-Fatal+ Fatal+ Unsupported-
RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
MaxPayload 256 bytes, MaxReadReq 512 bytes
DevSta: CorrErr+ UncorrErr- FatalErr- UnsuppReq+ AuxPwr- TransPend-
LnkCap: Port #16, Speed 8GT/s, Width x16, ASPM not supported, Exit Latency
L0s <1us, L1 <4us
ClockPM+ Surprise- LLActRep- BwNot- ASPMOptComp+
LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- CommClk-
ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
LnkSta: Speed 8GT/s, Width x16, TrErr- Train- SlotClk+ DLActive- BWMgmt-
ABWMgmt-
DevCap2: Completion Timeout: Range AB, TimeoutDis+, LTR+, OBFF Via message
DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR-, OBFF Disabled
LnkCtl2: Target Link Speed: 8GT/s, EnterCompliance- SpeedDis-
Transmit Margin: Normal Operating Range, EnterModifiedCompliance-
ComplianceSOS-
Compliance De-emphasis: -6dB
LnkSta2: Current De-emphasis Level: -6dB, EqualizationComplete+,
EqualizationPhase1+
EqualizationPhase2+, EqualizationPhase3+, LinkEqualizationRequest-
Capabilities: [100 v1] Virtual Channel
Caps: LPEVC=0 RefClk=100ns PATEntryBits=1
Arb: Fixed- WRR32- WRR64- WRR128-
Ctrl: ArbSelect=Fixed
Status: InProgress-
VC0: Caps: PATOffset=00 MaxTimeSlots=1 RejSnoopTrans-
Arb: Fixed- WRR32- WRR64- WRR128- TWRR128- WRR256-
Ctrl: Enable+ ID=0 ArbSelect=Fixed TC/VC=ff
Status: NegoPending- InProgress-
Capabilities: [250 v1] Latency Tolerance Reporting
Max snoop latency: 0ns
Max no snoop latency: 0ns
Capabilities: [258 v1] L1 PM Substates
L1SubCap: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2- ASPM_L1.1- L1_PM_Substates+
Capabilities: [128 v1] Power Budgeting <?>
Capabilities: [420 v2] Advanced Error Reporting
UESta: DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP-
ECRC- UnsupReq- ACSViol-
UEMsk: DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP-
ECRC- UnsupReq- ACSViol-
UESvrt: DLP+ SDES+ TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+
ECRC- UnsupReq- ACSViol-
CESta: RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr-
CEMsk: RxErr- BadTLP- BadDLLP- Rollover- Timeout- NonFatalErr+
AERCap: First Error Pointer: 00, GenCap- CGenEn- ChkCap- ChkEn-
Capabilities: [600 v1] Vendor Specific Information: ID=0001 Rev=1 Len=024
<?>
Capabilities: [900 v1] #19
Kernel driver in use: vfio-pci
Kernel modules: nouveau