linux-kernel - Re: [patch for-5.8] dma-pool: decouple DMA_REMAP from DMA_COHERENT

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Date:   Thu, 11 Jun 2020 10:49:53 -0400
From:   "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>
To:     Christoph Hellwig <hch@....de>,
        David Rientjes <rientjes@...gle.com>
Cc:     alsa-devel@...a-project.org, bp@...en8.de, hch@...radead.org,
        hpa@...or.com, linux-kernel@...r.kernel.org, mingo@...hat.com,
        Pavel Machek <pavel@....cz>, perex@...ex.cz,
        tglx@...utronix.de, tiwai@...e.com, x86@...nel.org
Subject: Re: [patch for-5.8] dma-pool: decouple DMA_REMAP from
 DMA_COHERENT_POOL

Excerpts from David Rientjes's message of June 11, 2020 3:25 am:
> DMA_REMAP is an unnecessary requirement for AMD SEV, which requires 
> DMA_COHERENT_POOL, so avoid selecting it when it is otherwise unnecessary.  
> 
> The only other requirement for DMA coherent pools is DMA_DIRECT_REMAP, so 
> ensure that properly selects the config option when needed.
> 
> Fixes: 82fef0ad811f ("x86/mm: unencrypted non-blocking DMA allocations use 
> coherent pools")
> Suggested-by: Christoph Hellwig <hch@....de>
> Signed-off-by: David Rientjes <rientjes@...gle.com>
> ---
>  kernel/dma/Kconfig | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 

Works for me with SME on or off with af7b480103, and with SME off in 
abfbb29297. There is some regression with amdgpu and SME between those 
two points, I need to check that out too. I haven't tested either before 
or after with SEV (which I'm not even sure my system supports). 
Regardless, this is a definite improvement.

Tested-by: Alex Xu (Hello71) <alex_y_xu@...oo.ca>

Thanks,
Alex.