linux-kernel - Re: [Regression] "iommu/amd: Relax locking in dma_ops path" makes tg3 ethernet transmit queue timeout

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Date:   Mon, 18 May 2020 23:32:02 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     iommu@...ts.linux-foundation.org,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [Regression] "iommu/amd: Relax locking in dma_ops path" makes tg3
 ethernet transmit queue timeout



> On May 18, 2020, at 22:05, Kai-Heng Feng <kai.heng.feng@...onical.com> wrote:
> 
> 
> 
>> On May 18, 2020, at 21:32, Joerg Roedel <jroedel@...e.de> wrote:
>> 
>> On Mon, May 18, 2020 at 05:06:45PM +0800, Kai-Heng Feng wrote:
>>> Particularly, as soon as the spinlock is removed, the issue can be reproduced.
>>> Function domain_flush_complete() doesn't seem to affect the status.
>>> 
>>> However, the .map_page callback was removed by be62dbf554c5
>>> ("iommu/amd: Convert AMD iommu driver to the dma-iommu api"), so
>>> there's no easy revert for this issue.
>>> 
>>> This is still reproducible as of today's mainline kernel, v5.7-rc6.
>> 
>> Is there any error message from the IOMMU driver?
>> 
> 
> As of mainline kernel, there's no error message from IOMMU driver.
> There are some complains from v4.15-rc1:
> https://pastebin.ubuntu.com/p/qn4TXkFxsc/

Just tested v5.7-rc6, the issue disappears as soon as kernel boots with "iommu=off".

Kai-Heng

> 
> Kai-Heng