Re: [dpdk-dev] [PATCH 3/7] mem: add function for setting DMA mask

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

On 31-Oct-18 5:29 PM, Alejandro Lucero wrote:
> This patch adds the possibility of setting a dma mask to be used
> once the memory initialization is done.
> 
> This is currently needed when IOVA mode is set by PCI related
> code and an x86 IOMMU hardware unit is present. Current code calls
> rte_mem_check_dma_mask but it is wrong to do so at that point
> because the memory has not been initialized yet.
> 
> Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com>
> ---
>   lib/librte_eal/common/eal_common_memory.c  | 10 ++++++++++
>   lib/librte_eal/common/include/rte_memory.h | 10 ++++++++++
>   lib/librte_eal/rte_eal_version.map         |  1 +
>   3 files changed, 21 insertions(+)
> 
> diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
> index e0f08f39a..24b72fcb0 100644
> --- a/lib/librte_eal/common/eal_common_memory.c
> +++ b/lib/librte_eal/common/eal_common_memory.c
> @@ -480,6 +480,16 @@ rte_mem_check_dma_mask(uint8_t maskbits)
>   	return 0;
>   }
>   
> +/* set dma mask to use when memory initialization is done */
> +void __rte_experimental
> +rte_mem_set_dma_mask(uint8_t maskbits)
> +{
> +	struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
> +
> +	mcfg->dma_maskbits = mcfg->dma_maskbits == 0 ? maskbits :
> +			     RTE_MIN(mcfg->dma_maskbits, maskbits);
> +}
> +
>   /* return the number of memory channels */
>   unsigned rte_memory_get_nchannel(void)
>   {
> diff --git a/lib/librte_eal/common/include/rte_memory.h b/lib/librte_eal/common/include/rte_memory.h
> index ad3f3cfb0..eff028db1 100644
> --- a/lib/librte_eal/common/include/rte_memory.h
> +++ b/lib/librte_eal/common/include/rte_memory.h
> @@ -466,6 +466,16 @@ unsigned rte_memory_get_nrank(void);
>   /* check memsegs iovas are within a range based on dma mask */
>   int __rte_experimental rte_mem_check_dma_mask(uint8_t maskbits);
>   
> +/**
> + *  * @warning
> + * @b EXPERIMENTAL: this API may change without prior notice

I think there's a copy-paste error here (extra star and indent before 
warning).

> + *
> + *  Set dma mask to use once memory initialization is done.
> + *  Previous function rte_mem_check_dma_mask can not be used
> + *  safely until memory has been initialized.

IMO this really requires a big bold warning saying that this function 
must only be called early during initialization, before memory is 
initialized, and not to be called in user code.

> + */
> +void __rte_experimental rte_mem_set_dma_mask(uint8_t maskbits);
> +
>   /**
>    * Drivers based on uio will not load unless physical
>    * addresses are obtainable. It is only possible to get
> diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
> index ef8126a97..ae24b5c73 100644
> --- a/lib/librte_eal/rte_eal_version.map
> +++ b/lib/librte_eal/rte_eal_version.map
> @@ -296,6 +296,7 @@ EXPERIMENTAL {
>   	rte_devargs_remove;
>   	rte_devargs_type_count;
>   	rte_mem_check_dma_mask;
> +	rte_mem_set_dma_mask;

Same, this needs to be alphabetic.

>   	rte_eal_cleanup;
>   	rte_fbarray_attach;
>   	rte_fbarray_destroy;
> 


-- 
Thanks,
Anatoly