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

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Wed, 1 Nov 2017 01:07:26 +0000
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> To: Thomas Monjalon <thomas@monjalon.net>, Bruce Richardson
>  <bruce.richardson@intel.com>, Sergio Gonzalez Monroy
>  <sergio.gonzalez.monroy@intel.com>
> CC: dev@dpdk.org, Ferruh Yigit <ferruh.yigit@intel.com>, Jianfeng Tan
>  <jianfeng.tan@intel.com>, Santosh Shukla
>  <santosh.shukla@caviumnetworks.com>
> Subject: [dpdk-dev] [PATCH] eal: disable IOVA mode detection by default
> X-Mailer: git-send-email 2.13.6
> 
> Fix kernel crash with KNI because KNI requires physical addresses.

The actual fix would be to make KNI IOMMU aware based on the DPDK mode.

ie. On slow path,

/* Get iommu domain for iova to physical addr conversion */             
if (rte_eal_iova_mode() == RTE_IOVA_VA)
	kni->iommu_domain = iommu_get_domain_for_dev(dev);
else
	kni->iommu_domain = NULL;

On fast path,

static inline u64 kni_iova_to_phys(struct ... *kni, dma_addr_t dma_addr)    
{                                                                               
        /* Translation is installed only when IOMMU is present */               
        if (kni->iommu_domain)                                                  
                return iommu_iova_to_phys(kni->iommu_domain, dma_addr);         
        return dma_addr;                                                        
} 

> 
> 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>
> ---
> Cc: Jianfeng Tan <jianfeng.tan@intel.com>
> Cc: Santosh Shukla <santosh.shukla@caviumnetworks.com>
> Cc: Thomas Monjalon <thomas@monjalon.net>
> ---
>  config/common_base                | 5 +++++
>  lib/librte_eal/bsdapp/eal/eal.c   | 4 ++++
>  lib/librte_eal/linuxapp/eal/eal.c | 4 ++++
>  3 files changed, 13 insertions(+)
> 
> diff --git a/config/common_base b/config/common_base
> index 82ee75456..903e7685b 100644
> --- a/config/common_base
> +++ b/config/common_base
> @@ -107,6 +107,11 @@ CONFIG_RTE_MALLOC_DEBUG=n
>  CONFIG_RTE_EAL_NUMA_AWARE_HUGEPAGES=n
>  
>  #
> +# Disabling PHYS_IOVA may crash kernel for KNI, use with caution
> +#
> +CONFIG_RTE_EAL_USE_PHYS_IOVA=y

Defeat the purpose of all dynamic probing scheme.
Either we can fix the KNI or revert the following patch for this release.

http://dpdk.org/commit/f37dfab2