Re: [dpdk-dev] [PATCH 4/7] bus/pci: avoid call to DMA mask check

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 31-Oct-18 5:29 PM, Alejandro Lucero wrote:
> Calling rte_mem_check_dma_mask when memory has not been initialized
> yet is wrong. This patch use rte_mem_set_dma_mask instead.
> 
> Once memory initialization is done, the dma mask set will be used
> for checking memory mapped is within the specified mask.
> 
> Fixes: fe822eb8c565 ("bus/pci: use IOVA DMA mask check when setting IOVA mode")
> 
> Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com>
> ---
>   drivers/bus/pci/linux/pci.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
> index 0a81e063b..d87384c72 100644
> --- a/drivers/bus/pci/linux/pci.c
> +++ b/drivers/bus/pci/linux/pci.c
> @@ -590,7 +590,16 @@ pci_one_device_iommu_support_va(struct rte_pci_device *dev)
>   
>   	mgaw = ((vtd_cap_reg & VTD_CAP_MGAW_MASK) >> VTD_CAP_MGAW_SHIFT) + 1;
>   
> -	return rte_mem_check_dma_mask(mgaw) == 0 ? true : false;
> +	/*
> +	 * Assuming there is no limitation by now. We can not know at this point
> +	 * because the memory has not been initialized yet. Setting the dma mask
> +	 * will force a check once memory initialization is done. We can not do
> +	 * a fallback to IOVA PA now, but if the dma check fails, the error
> +	 * message should advice for using '--iova-mode pa' if IOVA VA is the
> +	 * current mode.
> +	 */
> +	rte_mem_set_dma_mask(mgaw);
> +	return true;

This is IMO a good solution to the circular dependency between setting 
DMA mask and memory init. At least i can't think of a better one :)

Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>

>   }
>   #elif defined(RTE_ARCH_PPC_64)
>   static bool
> 


-- 
Thanks,
Anatoly