From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Monjalon <thomas@monjalon.net>
Subject: Re: [PATCH] eal: disable IOVA mode detection by default
Date: Wed, 01 Nov 2017 11:31:16 +0100
Message-ID: <79461063.5rUd41U7jB@xps>
References: <20171101010726.17781-1-ferruh.yigit@intel.com>
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Cc: Bruce Richardson <bruce.richardson@intel.com>,
 Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>, dev@dpdk.org,
 Jianfeng Tan <jianfeng.tan@intel.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>,
 Santosh Shukla <santosh.shukla@caviumnetworks.com>,
 jerin.jacob@caviumnetworks.com
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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?