On 06-Sep-18 8:34 AM, Jerin Jacob wrote:

-----Original Message-----

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Date: Tue, 4 Sep 2018 23:40:36 -0400
From: Eric Zhang <redacted>
To: santosh <redacted>, hemant.agrawal@nxp.com,
  Gaëtan Rivet [off-list ref], "Burakov, Anatoly"
  [off-list ref]
CC: bruce.richardson@intel.com, dev@dpdk.org, Allain.Legacy@windriver.com,
  Matt.Peters@windriver.com
Subject: Re: [dpdk-dev] [PATCH] eal: force IOVA mode to physical
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On 08/30/2018 08:59 AM, santosh wrote:

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On Thursday 30 August 2018 05:43 PM, Hemant wrote:

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External Email

Hi,

On 8/30/2018 3:13 PM, Gaëtan Rivet wrote:

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Hi,

On Thu, Aug 30, 2018 at 10:09:04AM +0100, Burakov, Anatoly wrote:

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On 29-Aug-18 4:58 PM, eric zhang wrote:

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This patch adds a configuration option to force the IOVA mode to
physical address (PA). There exists virtual devices that are not
directly attached to the PCI bus, and therefore the auto detection
of the IOVA mode based on probing the PCI bus and IOMMU configuration
may not report the required addressing mode. Having the configuration
option permits the mode to be explicitly configured in this scenario.

Signed-off-by: eric zhang <redacted>
---

Defining this at compile-time seems like an overkill. Wouldn't it be better
to just add an EAL command-line option to force IOVA mode to a particular
value?

That is a good suggestion.

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--
Thanks,
Anatoly

What is the bus of these devices and why not implement get_iommu_class
in it?

There are cases, where you are using dpdk libraries with external
libraries and you need to change the default behavior DPDK lib to use
physical address instead of virtual address.
Providing an option to user will help.

More appropriate solution could be:
* Either fix it at bus layer .. i.e.. get_iommu_class()..
* Or introduce something like [1] --iova-mode=<pa/va> param.

Former is better solution than latter if autodetection is a key criteria.
Thanks.

[1] http://patchwork.dpdk.org/patch/25192/

It's not generic which couldn't be fixed at bus layer.
So what's the preference of EAL option or compile time solution?
Adding --iova-mode as patch [1] will overrivde auto-detection
rte_bus_get_iommu_class()
make it no use; compile time solution will align with upstream and keep
new atuodetection
solution in #ifndef.

If it is for vdev devices, why not introduce something like
RTE_PCI_DRV_IOVA_AS_VA and let vdev device describe its personality.
And based on the devices(flags) on vdev bus, rte_bus_get_iommu_class()
of vdev can decide the mode just like PCI bus.

That seems like a better option to me, +1. As far as i know, at the 
moment if there are no devices attached at all, or if there are only 
vdev devices attached, DPDK will default to IOVA as PA mode for no good 
reason; such a change would certainly fix this.

quoted

Thanks
Eric

-- 
Thanks,
Anatoly