Re: [PATCH 21/33] dma-mapping: add an arch_dma_supported hook

Konrad Rzeszutek Wilk
2018-01-12T13:17:28Z

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@lst.de>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.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
>