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Date: Tue, 20 May 2014 04:23:23 -0700
From: Stephen Hemminger <stephen@networkplumber.org>
To: "Burakov, Anatoly" <anatoly.burakov@intel.com>
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Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v2 10/16] Added support for selecting VFIO
 interrupt type from EAL command-line
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On Tue, 20 May 2014 08:33:43 +0000
"Burakov, Anatoly" <anatoly.burakov@intel.com> wrote:

> Hi Stephen,
> 
> > I really wish the code did automatic fall back based on PCI config. It is possible to know the right mode, and do the right thing.
> > Rather than punting the problem out to command line which is totally unusable in hot plug and generic application.
> 
> You mean we should use whatever is available rather than default to MSI-X if nothing was explicitly specified? That could be done, I guess.
> 
> Best regards,
> Anatoly Burakov
> DPDK SW Engineer
> 
> 

I am not sure that MSI-X has any advantage with only one IRQ, so MSI would do.
Then have the code look at the PCI capability of device and fallback to INTX
if needed. It should also check if INTX works, see kernel for details, since
some PCI emulation like VMware is broken.