Implementing .shutdown method for efa module

[Jason Gunthorpe]

On Tue, Mar 26, 2024 at 02:34:45PM +0200, Margolin, Michael wrote:
> Hi Tao,
> 
> Thanks for bringing this up.
> 
> I've unsuccessfully tried to reproduce this kernel panic using production
> Red Hat 9.3 AMI (5.14.0-362.18.1.el9_3.aarch64).
> 
> Are there any related changes in the kernel you are testing?
> 
> Anyways we do need to handle shutdown properly, please let know if calling
> to efa_remove solves your issue.

efa_remove should not be used for shutdown..

If you have an iommu in your system (smmuv3 for this ARM64 case) then
drivers must implement a shutdown handler or you will risk data
corruption on ARM64 sytems during crash.

The shutdown handler must stop all DMA from the device.

If you don't have an iommu then the shutdown handler shouldn't be
critical.

Jason