linux-kernel - Re: [PATCH v3 3/6] dma-mapping: Remove dma_check

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Date:   Thu, 18 Jul 2019 17:29:30 +0000
From:   "Lendacky, Thomas" <Thomas.Lendacky@....com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        "x86@...nel.org" <x86@...nel.org>
CC:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Mike Anderson <andmike@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>
Subject: Re: [PATCH v3 3/6] dma-mapping: Remove dma_check_mask()

On 7/17/19 10:28 PM, Thiago Jung Bauermann wrote:
> sme_active() is an x86-specific function so it's better not to call it from
> generic code. Christoph Hellwig mentioned that "There is no reason why we
> should have a special debug printk just for one specific reason why there
> is a requirement for a large DMA mask.", so just remove dma_check_mask().
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>  kernel/dma/mapping.c | 8 --------
>  1 file changed, 8 deletions(-)
> 
> diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> index 1f628e7ac709..61eeefbfcb36 100644
> --- a/kernel/dma/mapping.c
> +++ b/kernel/dma/mapping.c
> @@ -291,12 +291,6 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
>  }
>  EXPORT_SYMBOL(dma_free_attrs);
>  
> -static inline void dma_check_mask(struct device *dev, u64 mask)
> -{
> -	if (sme_active() && (mask < (((u64)sme_get_me_mask() << 1) - 1)))
> -		dev_warn(dev, "SME is active, device will require DMA bounce buffers\n");
> -}
> -
>  int dma_supported(struct device *dev, u64 mask)
>  {
>  	const struct dma_map_ops *ops = get_dma_ops(dev);
> @@ -327,7 +321,6 @@ int dma_set_mask(struct device *dev, u64 mask)
>  		return -EIO;
>  
>  	arch_dma_set_mask(dev, mask);
> -	dma_check_mask(dev, mask);
>  	*dev->dma_mask = mask;
>  	return 0;
>  }
> @@ -345,7 +338,6 @@ int dma_set_coherent_mask(struct device *dev, u64 mask)
>  	if (!dma_supported(dev, mask))
>  		return -EIO;
>  
> -	dma_check_mask(dev, mask);
>  	dev->coherent_dma_mask = mask;
>  	return 0;
>  }
>