On Fri, 14 Jun 2013 17:09:49 +0000
"Skidmore, Donald C" <[email protected]> wrote:

> We haven't implemented this as you know so I haven't looked in to it
> at all in detail but off the top of my head:
> 
> There is only one interrupt with MSI per say, as John mentioned.  So
> you will either have to only get all interrupts in the PF and have it
> tell the VF who they belonged to, nasty latency if doable at all.  Or
> have all VF's and the PF interrupted for any interrupt that was
> destine for any VF or the PF.  This second choice would be a lot of
> overhead and also would mean any VF would know when other VF's were
> getting interrupts (security issue?). 

The VF cannot send MSI interrupts, period.  It is a HW limitation -
they only support MSIX.  It is not possible to use MSI with Intel VF
devices in any way or manner.

- Greg

> 
> Thanks,
> -Don Skidmore <[email protected]>
> 
> > -----Original Message-----
> > From: mhban [mailto:[email protected]]
> > Sent: Thursday, June 13, 2013 7:50 PM
> > To: Ronciak, John; Skidmore, Donald C; Kirsher, Jeffrey T
> > Cc: [email protected]; Brandeburg, Jesse
> > Subject: RE: [E1000-devel] Regarding 82599 SR-IOV support in MSI
> > 
> > Dear John and Don,
> > Thanks for kind reply.
> > 
> > This ARM SoC doesn't have additional features for virtualization
> > like VT-d. And I'm not going to use SR-IOV for virtualization. I
> > just want to do some experimental VF test only with limited 2 or 4.
> > 
> > BTW, I have one more question about this.
> > Do you mean root-port can receive interrupt from VFs that are
> > configured as MSI mode?
> > If so, is it possible to differentiate between them? For example,
> > by reading flag registers again or something like that.
> > 
> > 
> > 
> > -----Original Message-----
> > From: Ronciak, John [mailto:[email protected]]
> > Sent: Friday, June 14, 2013 12:13 AM
> > To: Skidmore, Donald C; mhban; Kirsher, Jeffrey T
> > Cc: [email protected]; Brandeburg, Jesse
> > Subject: RE: [E1000-devel] Regarding 82599 SR-IOV support in MSI
> > 
> > Hello,
> > 
> > No it's not possible.  MSI-X is needed so that interrupts can be
> > routed to each guest.  With MSI there is only a single interrupt so
> > there is no way to route it to multiple VF's.  MSI-X is a
> > requirement for SR-IOV support.  So don's comments below are
> > correct.  Sorry.
> > 
> > Does this system support VT-d or something like it for the address
> > translations?  Just curious.
> > 
> > Cheers,
> > John
> > 
> > Cheers,
> > John
> > 
> > 
> > > -----Original Message-----
> > > From: Skidmore, Donald C [mailto:[email protected]]
> > > Sent: Thursday, June 13, 2013 7:17 AM
> > > To: mhban; Kirsher, Jeffrey T
> > > Cc: [email protected]; Brandeburg, Jesse
> > > Subject: Re: [E1000-devel] Regarding 82599 SR-IOV support in MSI
> > >
> > > Hey Minho,
> > >
> > > I believe that it would be problematic at best since as MSI uses
> > > identical address for all vectors in a Function and differentiates
> > > vectors in a Function only by LSBs in data.
> > >
> > > Thanks,
> > > -Don Skidmore <[email protected]>
> > >
> > > > -----Original Message-----
> > > > From: mhban [mailto:[email protected]]
> > > > Sent: Thursday, June 13, 2013 12:40 AM
> > > > To: Kirsher, Jeffrey T
> > > > Cc: [email protected]; Brandeburg, Jesse
> > > > Subject: [E1000-devel] Regarding 82599 SR-IOV support in MSI
> > > >
> > > > Dear maintainer and all SR-IOV experts,
> > > >
> > > > I'm developing a board which is based on ARM SoC which support
> > > > PCI Express root-port.
> > > > I'm trying to install and activate SR-IOV with Intel X520-SR2 on
> > > > this board(/w Linux). Up to now, ixgbe and ixgbevf driver is
> > > > loaded successfully but driver prints error when I try to do
> > > > 'ifup'.
> > > >
> > > >          "PF still in reset state".
> > > >
> > > > While debugging it I found one important article from Intel
> > > > community site,
> > > >
> > > >         http://communities.intel.com/message/158673#158673
> > > >
> > > > I realized Intel 82599 require MSI-X for SR-IOV not MSI, but
> > > > the ARM SoC only support MSI.
> > > > What I want to know is if it is possible to activate SR-IOV
> > > > with MSI (not MSI- X). I know ixgbevf officially doesn't
> > > > support MSI for SR-
> > > IOV
> > > > but I just want to use it for experimental test on the ARM
> > > > environment. According to the article, it seems there was no
> > > > hardware limitation which  prevent the use of MSI. If so, can I
> > > > make work SR-IOV using MSI instead of MSI-X by little re- work
> > > > ixgbevf(or ixgbe
> > > also) driver?
> > > >
> > > > Please shed some light on this.
> > > >
> > > > Best regards,
> > > > Minho Ban
> > > >
> > > > SAMSUNG Electronics, Co., Ltd.
> > > > (Office) +82-31-301-8489  (Mobile) +82-10-8725-8864
> > > >
> > > >
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