linux-kernel - Re: [PATCH 21/33] dma-mapping: add an arch_dma

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Message-ID: <20180112131727.GB26900@localhost.localdomain>
Date:   Fri, 12 Jan 2018 08:17:28 -0500
From:   Konrad Rzeszutek Wilk <konrad@...nok.org>
To:     Christoph Hellwig <hch@....de>
Cc:     iommu@...ts.linux-foundation.org, linux-alpha@...r.kernel.org,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-c6x-dev@...ux-c6x.org,
        linux-cris-kernel@...s.com, linux-hexagon@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
        linux-metag@...r.kernel.org, Michal Simek <monstr@...str.eu>,
        linux-mips@...ux-mips.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, patches@...ups.riscv.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, Guan Xuetao <gxt@...c.pku.edu.cn>,
        x86@...nel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 21/33] dma-mapping: add an arch_dma_supported hook

On Wed, Jan 10, 2018 at 09:00:15AM +0100, Christoph Hellwig wrote:
> To implement the x86 forbid_dac and iommu_sac_force we want an arch hook
> so that it can apply the global options across all dma_map_ops
> implementations.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  arch/x86/include/asm/dma-mapping.h |  3 +++
>  arch/x86/kernel/pci-dma.c          | 19 ++++++++++++-------
>  include/linux/dma-mapping.h        | 11 +++++++++++
>  3 files changed, 26 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h
> index dfdc9357a349..6277c83c0eb1 100644
> --- a/arch/x86/include/asm/dma-mapping.h
> +++ b/arch/x86/include/asm/dma-mapping.h
> @@ -30,6 +30,9 @@ static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
>  	return dma_ops;
>  }
>  
> +int arch_dma_supported(struct device *dev, u64 mask);
> +#define arch_dma_supported arch_dma_supported
> +
>  bool arch_dma_alloc_attrs(struct device **dev, gfp_t *gfp);
>  #define arch_dma_alloc_attrs arch_dma_alloc_attrs
>  
> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
> index 61a8f1cb3829..df7ab02f959f 100644
> --- a/arch/x86/kernel/pci-dma.c
> +++ b/arch/x86/kernel/pci-dma.c
> @@ -215,7 +215,7 @@ static __init int iommu_setup(char *p)
>  }
>  early_param("iommu", iommu_setup);
>  
> -int x86_dma_supported(struct device *dev, u64 mask)
> +int arch_dma_supported(struct device *dev, u64 mask)
>  {
>  #ifdef CONFIG_PCI
>  	if (mask > 0xffffffff && forbid_dac > 0) {
> @@ -224,12 +224,6 @@ int x86_dma_supported(struct device *dev, u64 mask)
>  	}
>  #endif
>  
> -	/* Copied from i386. Doesn't make much sense, because it will
> -	   only work for pci_alloc_coherent.
> -	   The caller just has to use GFP_DMA in this case. */
> -	if (mask < DMA_BIT_MASK(24))
> -		return 0;
> -
>  	/* Tell the device to use SAC when IOMMU force is on.  This
>  	   allows the driver to use cheaper accesses in some cases.
>  
> @@ -249,6 +243,17 @@ int x86_dma_supported(struct device *dev, u64 mask)
>  
>  	return 1;
>  }
> +EXPORT_SYMBOL(arch_dma_supported);
> +
> +int x86_dma_supported(struct device *dev, u64 mask)
> +{
> +	/* Copied from i386. Doesn't make much sense, because it will
> +	   only work for pci_alloc_coherent.
> +	   The caller just has to use GFP_DMA in this case. */
> +	if (mask < DMA_BIT_MASK(24))
> +		return 0;
> +	return 1;
> +}
>  
>  static int __init pci_iommu_init(void)
>  {
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 88bcb1a8211d..d67742dad904 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -576,6 +576,14 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
>  	return 0;
>  }
>  
> +/*
> + * This is a hack for the legacy x86 forbid_dac and iommu_sac_force. Please
> + * don't use this is new code.
> + */
> +#ifndef arch_dma_supported
> +#define arch_dma_supported(dev, mask)	(1)
> +#endif
> +
>  static inline void dma_check_mask(struct device *dev, u64 mask)
>  {
>  	if (sme_active() && (mask < (((u64)sme_get_me_mask() << 1) - 1)))
> @@ -588,6 +596,9 @@ static inline int dma_supported(struct device *dev, u64 mask)
>  
>  	if (!ops)
>  		return 0;
> +	if (!arch_dma_supported(dev, mask))
> +		return 0;
> +
>  	if (!ops->dma_supported)
>  		return 1;
>  	return ops->dma_supported(dev, mask);
> -- 
> 2.14.2
>