Kernel and ADM hardware roulette ( was AMD graphics performance regression in 4.15 and later )

[Christian König]

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 at lst.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 at amd.com>
>>     Tested-by: Joerg Roedel <jroedel at suse.de>
>>     Signed-off-by: Christoph Hellwig <hch at lst.de>
>>     Reviewed-by: Thomas Gleixner <tglx at linutronix.de>
>>     Acked-by: Joerg Roedel <jroedel at suse.de>
>>     Cc: David Woodhouse <dwmw2 at infradead.org>
>>     Cc: Joerg Roedel <joro at 8bytes.org>
>>     Cc: Jon Mason <jdmason at kudzu.us>
>>     Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
>>     Cc: Linus Torvalds <torvalds at linux-foundation.org>
>>     Cc: Muli Ben-Yehuda <mulix at mulix.org>
>>     Cc: Peter Zijlstra <peterz at infradead.org>
>>     Cc: iommu at lists.linux-foundation.org
>>     Link: http://lkml.kernel.org/r/20180319103826.12853-8-hch@lst.de
>>     Signed-off-by: Ingo Molnar <mingo at kernel.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