linux-kernel - Re: Implementing .shutdown method for efa module

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Message-ID: <0e7dddff-d7f3-4617-83e6-f255449a282b@amazon.com>
Date: Mon, 1 Apr 2024 16:23:32 +0300
From: "Margolin, Michael" <mrgolin@...zon.com>
To: Jason Gunthorpe <jgg@...pe.ca>
CC: Tao Liu <ltao@...hat.com>, Gal Pressman <gal.pressman@...ux.dev>,
	<sleybo@...zon.com>, <leon@...nel.org>, <kexec@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-rdma@...r.kernel.org>
Subject: Re: Implementing .shutdown method for efa module

Jason

Thanks for your response, efa_remove() is performing reset to the device 
which should stop all DMA from the device.

Except skipping cleanups that are unnecessary for shutdown flow are 
there any other reasons to prefer a separate function for shutdown?


Michael

On 3/26/2024 5:32 PM, Jason Gunthorpe wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
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>
>
> 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