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Hi, I start a virtual machine with commandline: /usr/libexec/qemu-kvm --enable-kvm -smp 8 -m 8192 -device vfio-pci,host=0000:81:00.0 Then I pause the qemu process before executing the main_loop function by gdb. At this moment, lspci shows the regions are disabled like below: 81:00.0 3D controller: NVIDIA Corporation GP100GL [Tesla P100 PCIe 16GB] (rev a1) Subsystem: NVIDIA Corporation Device 118f Physical Slot: 0-6 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- Interrupt: pin A routed to IRQ 35 NUMA node: 1 Region 0: Memory at c8000000 (32-bit, non-prefetchable) [disabled] [size=16M] Region 1: Memory at 27800000000 (64-bit, prefetchable) [disabled] [size=16G] Region 3: Memory at 27c00000000 (64-bit, prefetchable) [disabled] [size=32M] But after the command: echo 1 > /sys/bus/pci/devices/0000:81:00.0/reset lspci shows the regions are
*not* disabled: 81:00.0 3D controller: NVIDIA Corporation GP100GL [Tesla P100 PCIe 16GB] (rev a1) Subsystem: Huawei Technologies Co., Ltd. Device 2061 Physical Slot: 0-6 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: 1 Region 0: Memory at c8000000 (32-bit, non-prefetchable) [size=16M] Region 1: Memory at 27800000000 (64-bit, prefetchable) [size=16G] Region 3: Memory at 27c00000000 (64-bit, prefetchable) [size=32M] AFAIK, qemu performs vfio_pci_reset like the below callstack: Qemu: vfio_pci_reset ioctl(vdev->vbasedev.fd, VFIO_DEVICE_RESET) Kernel: vfio_pci_ioctl pci_try_reset_function __pci_reset_function_locked pci_parent_bus_reset pci_reset_bridge_secondary_bus and write 1 to the reset interface of sysfs go through the path: Kernel: reset_store pci_reset_function __pci_reset_function_locked pci_parent_bus_reset pci_reset_bridge_secondary_bus So seem that these two methods are same actually, I am confused why the results are inconsistent. Thanks, Zongyong Wu |
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