linux-kernel - Re: Kernel and ADM hardware roulette ( was AMD graphics performance regression in 4.15 and later )

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Date:   Thu, 7 Jun 2018 18:24:33 +0200
From:   Gabriel C <nix.or.die@...il.com>
To:     Christian König <christian.koenig@....com>
Cc:     Michel Dänzer <michel@...nzer.net>,
        Jean-Marc Valin <jmvalin@...illa.com>,
        Dave Airlie <airlied@...ux.ie>,
        Felix Kuehling <Felix.Kuehling@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org, alexander.deucher@....com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Joerg Roedel <jroedel@...e.de>, Christoph Hellwig <hch@....de>
Subject: Re: Kernel and ADM hardware roulette ( was AMD graphics performance
 regression in 4.15 and later )

>> Well that is very interesting, you are the first one who reports that SME +
>> GFX works in some way. So far we only got negative reports for that.
>>
>>> There is a 4.16.13 boot dmesg which has no such issue:
>>>
>>>
>>> http://ftp.frugalware.org/pub/other/people/crazy/radeon/dmesg-radeon-SME-ON-kernel-4.16.txt
>>>
>>> With the setup as is booting 4.16.x works , while 4.17 trows the errors.
>>
>>
>> Please do the bisect if the patch I've mentioned above doesn't help.
>
> Ok done.. bisect points to:
>
> b468620f2a1dfdcfddfd6fa54367b8bcc1b51248 is the first bad commit
> commit b468620f2a1dfdcfddfd6fa54367b8bcc1b51248
> Author: Christoph Hellwig <hch@....de>
> Date:   Mon Mar 19 11:38:19 2018 +0100
>
>    iommu/amd_iommu: Use CONFIG_DMA_DIRECT_OPS=y and dma_direct_{alloc,free}()
>
>    This cleans up the code a lot by removing duplicate logic.
>
>    Tested-by: Tom Lendacky <thomas.lendacky@....com>
>    Tested-by: Joerg Roedel <jroedel@...e.de>
>    Signed-off-by: Christoph Hellwig <hch@....de>
>    Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
>    Acked-by: Joerg Roedel <jroedel@...e.de>
>    Cc: David Woodhouse <dwmw2@...radead.org>
>    Cc: Joerg Roedel <joro@...tes.org>
>    Cc: Jon Mason <jdmason@...zu.us>
>    Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
>    Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>    Cc: Muli Ben-Yehuda <mulix@...ix.org>
>    Cc: Peter Zijlstra <peterz@...radead.org>
>    Cc: iommu@...ts.linux-foundation.org
>    Link: http://lkml.kernel.org/r/20180319103826.12853-8-hch@lst.de
>    Signed-off-by: Ingo Molnar <mingo@...nel.org>
>
>
> I'll try to revert this once I'm home.

I can confirm reverting b468620f2a1dfdcfddfd6fa54367b8bcc1b51248
fixes that issue for me.

The GPU is working fine with SME enabled.

Now with working GPU :) I can also confirm performance is back to normal
without doing any other workarounds.

The only app still acting up a bit is Firefox , just minor frame drops,
but nothing to bad.  ( probably an Firefox bug too )

crhomium/chrome is fine .. even with 10 tabs open , each one playing
an video on youtube no glitches at all.

Desktop is also fine now,  could not find anything wrong.


BR