Re: [PATCH] eal: disable IOVA mode detection by default

[Thomas Monjalon <thomas@monjalon.net>]

01/11/2017 02:07, Ferruh Yigit:
> Fix kernel crash with KNI because KNI requires physical addresses.
> 
> A config option introduced to disable IOVA mode detection and to set it
> to physical address by default. Disabling config option will enable IOVA
> mode detection.
> 
> When there is no intension to use KNI, it is safe to enable detection.
> 
> Config option disable IOVA mode detection by default to be sure only who
> is aware of result enable it.
> 
> Fixes: 72d013644bd6 ("mem: honor IOVA mode in malloc virt2phy")
> 
> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> ---
> +#ifdef RTE_EAL_USE_PHYS_IOVA
> +	rte_eal_get_configuration()->iova_mode = RTE_IOVA_PA;
> +#else
>  	/* autodetect the iova mapping mode (default is iova_pa) */
>  	rte_eal_get_configuration()->iova_mode = rte_bus_get_iommu_class();
> +#endif

I don't understand why you are adding a compile-time option.
I think it should be an EAL option --use-phys-addr.
The opposite option may be required to force VA: --use-virt-addr.
And if there is no option given, we fallback to autodetect.
We can improve the autodetect by checking whether rte_kni.ko is loaded.

Opinions?