Re: [dpdk-dev] [EXT] Re: [PATCH] bus/pci: fix IOVA as VA mode selection

From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>,
	David Marchand <david.marchand@redhat.com>
Cc: dev <dev@dpdk.org>, Thomas Monjalon <thomas@monjalon.net>,
	Ben Walker <benjamin.walker@intel.com>
Subject: Re: [dpdk-dev] [EXT] Re: [PATCH] bus/pci: fix IOVA as VA mode selection
Date: Tue, 9 Jul 2019 16:02:48 +0100	[thread overview]
Message-ID: <ce76637e-180b-247b-5703-85b7226b9af4@intel.com> (raw)
In-Reply-To: <BYAPR18MB2424B15F7CB2D9F46C4A26A8C8F10@BYAPR18MB2424.namprd18.prod.outlook.com>

On 09-Jul-19 3:58 PM, Jerin Jacob Kollanukkaran wrote:
>> -----Original Message-----
>> From: Burakov, Anatoly <anatoly.burakov@intel.com>
>> Sent: Tuesday, July 9, 2019 8:24 PM
>> To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; David Marchand
>> <david.marchand@redhat.com>
>> Cc: dev <dev@dpdk.org>; Thomas Monjalon <thomas@monjalon.net>; Ben
>> Walker <benjamin.walker@intel.com>
>> Subject: Re: [EXT] Re: [dpdk-dev] [PATCH] bus/pci: fix IOVA as VA mode
>> selection
>>
>> On 09-Jul-19 3:00 PM, Jerin Jacob Kollanukkaran wrote:
>>>> -----Original Message-----
>>>> From: Burakov, Anatoly <anatoly.burakov@intel.com>
>>>> Sent: Tuesday, July 9, 2019 7:00 PM
>>>> To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; David Marchand
>>>> <david.marchand@redhat.com>
>>>> Cc: dev <dev@dpdk.org>; Thomas Monjalon <thomas@monjalon.net>;
>> Ben
>>>> Walker <benjamin.walker@intel.com>
>>>> Subject: Re: [EXT] Re: [dpdk-dev] [PATCH] bus/pci: fix IOVA as VA
>>>> mode selection
>>>>
>>
>> <snip>
>>
>>>>
>>>>> # With top of tree, Currently it never runs in IOVA as VA mode.
>>>>> That’s a separate problem to fix. Which effect all the devices
>>>>> Currently supporting RTE_PCI_DRV_IOVA_AS_VA. Ie even though
>> Device
>>>>> support RTE_PCI_DRV_IOVA_AS_VA, it is not running With IOMMU
>>>>> protection and/or root privilege is required to run DPDK.
>>>
>>
>> By the way, there seems to be some confusion here. IOVA as PA mode does
>> *not* imply running without IOMMU protection. If IOVA as PA mode is used,
>> it would require root privileges (to get physical addresses), but the IOMMU
>> protection is still enabled. IOMMU doesn't care what you set up your
> 
> Yes. It was thinking more  of VFIO perspective. Not igb_uio.
> 

It is the same for both.

When IOMMU is fully enabled (iommu=on at boot time), igb_uio will simply 
not work. VFIO will work, whichever address mode you use.

When IOMMU is in pass-through mode (iommu=pt at boot time), both igb_uio 
and VFIO will work, although igb_uio will only support IOVA as PA mode. 
Both modes will enable IOMMU, and both can run in IOVA as PA mode 
without losing that protection.

It's only when IOMMU is off, igb_uio will not engage IOMMU, and VFIO 
will only work in no-IOMMU mode (thus not engaging IOMMU either), and 
only then you lack the IOMMU protection.

-- 
Thanks,
Anatoly