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 19:20:37 +0200
From:   Christian König <christian.koenig@....com>
To:     Gabriel C <nix.or.die@...il.com>, Christoph Hellwig <hch@....de>
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>
Subject: Re: Kernel and ADM hardware roulette ( was AMD graphics performance
 regression in 4.15 and later )

Hi Christopher,

Am 07.06.2018 um 18:24 schrieb Gabriel C:
>> [SNIP]
>> 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.

any idea what could cause that? Basically this patch breaks radeon when 
SME is enabled.

> 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.

Thanks for testing,
Christian.

>
>
> BR