RE: [PATCH v5 3/3] vfio/pci: Check the device set open count on reset

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Anthony DeRossi <ajderossi@gmail.com>
> Sent: Sunday, November 6, 2022 6:45 AM
> 
> vfio_pci_dev_set_needs_reset() inspects the open_count of every device
> in the set to determine whether a reset is allowed. The current device
> always has open_count == 1 within vfio_pci_core_disable(), effectively
> disabling the reset logic. This field is also documented as private in
> vfio_device, so it should not be used to determine whether other devices
> in the set are open.
> 
> Checking for vfio_device_set_open_count() > 1 on the device set fixes
> both issues.
> 
> After commit 2cd8b14aaa66 ("vfio/pci: Move to the device set
> infrastructure"), failure to create a new file for a device would cause
> the reset to be skipped due to open_count being decremented after
> calling close_device() in the error path.
> 
> After commit eadd86f835c6 ("vfio: Remove calls to
> vfio_group_add_container_user()"), releasing a device would always skip
> the reset due to an ordering change in vfio_device_fops_release().
> 
> Failing to reset the device leaves it in an unknown state, potentially
> causing errors when it is accessed later or bound to a different driver.
> 
> This issue was observed with a Radeon RX Vega 56 [1002:687f] (rev c3)
> assigned to a Windows guest. After shutting down the guest, unbinding
> the device from vfio-pci, and binding the device to amdgpu:
> 
> [  548.007102] [drm:psp_hw_start [amdgpu]] *ERROR* PSP create ring failed!
> [  548.027174] [drm:psp_hw_init [amdgpu]] *ERROR* PSP firmware loading
> failed
> [  548.027242] [drm:amdgpu_device_fw_loading [amdgpu]] *ERROR* hw_init
> of IP block <psp> failed -22
> [  548.027306] amdgpu 0000:0a:00.0: amdgpu: amdgpu_device_ip_init failed
> [  548.027308] amdgpu 0000:0a:00.0: amdgpu: Fatal error during GPU init
> 
> Fixes: 2cd8b14aaa66 ("vfio/pci: Move to the device set infrastructure")
> Fixes: eadd86f835c6 ("vfio: Remove calls to
> vfio_group_add_container_user()")
> Signed-off-by: Anthony DeRossi <ajderossi@gmail.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>