[PATCH v1 0/2] Add ablility of VFIO driver to ignore reset when device don't need it

[Zhenguo Yao <yaozhenguo1@gmail.com>]

In some scenarios, vfio device can't do any reset in initialization
process. For example: Nvswitch and GPU A100 working in Shared NVSwitch
Virtualization Model. In such mode, there are two type VMs: service
VM and Guest VM. The GPU devices are initialized in the following steps:

1. Service VM boot up. GPUs and Nvswitchs are passthrough to service VM.
Nvidia driver and manager software will do some settings in service VM.

2. The selected GPUs are unpluged from service VM.

3. Guest VM boots up with the selected GPUs passthrough.

The selected GPUs can't do any reset in step3, or they will be initialized
failed in Guest VM.

This patchset add a PCI sysfs interface:ignore_reset which drivers can
use it to control whether to do PCI reset or not. For example: In Shared
NVSwitch Virtualization Model. Hypervisor can disable PCI reset by setting
ignore_reset to 1 before Gust VM booting up.

Zhenguo Yao (2):
  PCI: Add ignore_reset sysfs interface to control whether do device
    reset in PCI drivers
  vfio-pci: Don't do device reset when ignore_reset is setting

 drivers/pci/pci-sysfs.c          | 25 +++++++++++++++++
 drivers/vfio/pci/vfio_pci_core.c | 48 ++++++++++++++++++++------------
 include/linux/pci.h              |  1 +
 3 files changed, 56 insertions(+), 18 deletions(-)

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2.27.0