[PATCH kernel v3 1/3] powerpc/iommu: Allow bypass-only for DMA

[David Gibson]

On Thu, May 30, 2019 at 05:03:53PM +1000, Alexey Kardashevskiy wrote:
> POWER8 and newer support a bypass mode which maps all host memory to
> PCI buses so an IOMMU table is not always required. However if we fail to
> create such a table, the DMA setup fails and the kernel does not boot.
> 
> This skips the 32bit DMA setup check if the bypass is can be selected.
> 
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>

Reviewed-by: David Gibson <david at gibson.dropbear.id.au>

> ---
> 
> This minor thing helped me debugging next 2 patches so it can help
> somebody else too.
> ---
>  arch/powerpc/kernel/dma-iommu.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c
> index 09231ef06d01..809c1dc01edf 100644
> --- a/arch/powerpc/kernel/dma-iommu.c
> +++ b/arch/powerpc/kernel/dma-iommu.c
> @@ -118,18 +118,17 @@ int dma_iommu_dma_supported(struct device *dev, u64 mask)
>  {
>  	struct iommu_table *tbl = get_iommu_table_base(dev);
>  
> -	if (!tbl) {
> -		dev_info(dev, "Warning: IOMMU dma not supported: mask 0x%08llx"
> -			", table unavailable\n", mask);
> -		return 0;
> -	}
> -
>  	if (dev_is_pci(dev) && dma_iommu_bypass_supported(dev, mask)) {
>  		dev->archdata.iommu_bypass = true;
>  		dev_dbg(dev, "iommu: 64-bit OK, using fixed ops\n");
>  		return 1;
>  	}
>  
> +	if (!tbl) {
> +		dev_err(dev, "Warning: IOMMU dma not supported: mask 0x%08llx, table unavailable\n", mask);
> +		return 0;
> +	}
> +
>  	if (tbl->it_offset > (mask >> tbl->it_page_shift)) {
>  		dev_info(dev, "Warning: IOMMU offset too big for device mask\n");
>  		dev_info(dev, "mask: 0x%08llx, table offset: 0x%08lx\n",

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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