Re: [PATCH kernel] powerpc/powernv/ioda: Fix endianness when reading TCEs

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Jul 20, 2016 at 02:26:51PM +1000, Alexey Kardashevskiy wrote:
> The iommu_table_ops::exchange() callback writes new TCE to the table
> and returns old value and permission mask. The old TCE value is
> correctly converted from BE to CPU endian; however permission mask
> was calculated from BE value and therefore always returned DMA_NONE
> which could cause memory leak on LE systems using VFIO SPAPR TCE IOMMU v1
> driver.
> 
> This fixes pnv_tce_xchg() to have @oldtce a CPU endian.
> 
> Fixes: 05c6cfb9dce0d13d37e9d007ee6a4af36f1c0a58
> Cc: stable@vger.kernel.org # 4.2+
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

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

> ---
>  arch/powerpc/platforms/powernv/pci.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
> index 1d92bd9..7b17f88 100644
> --- a/arch/powerpc/platforms/powernv/pci.c
> +++ b/arch/powerpc/platforms/powernv/pci.c
> @@ -620,8 +620,8 @@ int pnv_tce_xchg(struct iommu_table *tbl, long index,
>  	if (newtce & TCE_PCI_WRITE)
>  		newtce |= TCE_PCI_READ;
>  
> -	oldtce = xchg(pnv_tce(tbl, idx), cpu_to_be64(newtce));
> -	*hpa = be64_to_cpu(oldtce) & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +	oldtce = be64_to_cpu(xchg(pnv_tce(tbl, idx), cpu_to_be64(newtce)));
> +	*hpa = oldtce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
>  	*direction = iommu_tce_direction(oldtce);
>  
>  	return 0;

-- 
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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