Re: [Xen-devel] q35 in xen? vfio in xen?

["Zhang, Eniac" <eniac-xw.zhang@xxxxxx>]

Hi Konrad,

Thanks for the info.  Your guest sees the virtual function as  pci device just 
like I had suspected.  Unfortunately that won't work for me.  I guess I have to 
take a hard look at implement pci-e passthrough using pciback then.

Regards/Eniac

-----Original Message-----
From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx] 
Sent: Monday, February 24, 2014 9:40 AM
To: Zhang, Eniac
Cc: xen-devel@xxxxxxxxxxxxx
Subject: Re: [Xen-devel] q35 in xen? vfio in xen?

On Sat, Feb 22, 2014 at 08:06:50AM +0000, Zhang, Eniac wrote:
> Hi Konrad,
> 
> Here's what I see when start a VM under xen using pciback to pass a pci-e 
> device into domU.  The device can be seen by guest, and also functioning 
> fine.  But it's not seen as a pci-e device, rather, it looks just like an 
> ordinary pci device because only the first 0x100 bytes of its configuration 
> space is accessible.  So if a driver needs to use data in the extended 
> configuration space for certain features, it will fail.
> 
> When you say you "did PCIe pass through of an VF of an SR-IOV device".  Are 
> you actually using it as a pci-e device or have throttled it back to pci mode 
> without aware of the difference?  If you did see the pci-e device in guest, 
> can you share your xl.cfg file as well as lspci/lspci -t/lspci -xxxx output 
> from guest?

# lspci
00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
00:02.0 Class ff80: XenSource, Inc. Xen Platform Device (rev 01)
00:03.0 VGA compatible controller: Cirrus Logic GD 5446
00:04.0 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01) 
# lspci -t
-[0000:00]-+-00.0
           +-01.0
           +-01.1
           +-01.3
           +-02.0
           +-03.0
           \-04.0
# lspci -s 00:04.0 -xxxxx
00:04.0 Ethernet controller: Intel Corporation 82576 Virtual Function (rev 01)
00: 86 80 ca 10 06 04 10 00 01 00 00 02 00 00 00 00
10: 04 00 01 f3 00 00 00 00 00 00 00 00 04 40 01 f3
20: 00 00 00 00 00 00 00 00 00 00 00 00 86 80 3c a0
30: 00 00 00 00 70 00 00 00 00 00 00 00 00 00 00 00
40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
70: 11 a0 02 80 03 00 00 00 03 20 00 00 00 00 00 00
80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
a0: 10 00 02 00 c2 8c 00 00 10 28 00 00 41 6c 03 00
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
c0: 00 00 00 00 1f 00 00 00 00 00 00 00 00 00 00 00
d0: 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

-bash-4.1# more /vm-pci.cfg
builder='hvm'
disk = [ 'file:/mnt/lab/latest/root_image.iso,hdc:cdrom,r']
memory = 2048
boot="d"
maxvcpus=32
vcpus=1
serial='pty'
vnclisten="0.0.0.0"
name="latest"
pci = ["0000:02:10.0"]

> 
> Also to echo your second comment:  I might still be a newbie in qemu field (I 
> started working on this 4 months ago).  I thought the chipset limits what you 
> can see/do in vm.  Ie.  If you have 440fx emulations then you can't have any 
> pci-e devices (fake or passthru) in the same system.  Is that not true?
> 
> Regards/Eniac
> 
> -----Original Message-----
> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> Sent: Friday, February 21, 2014 5:32 PM
> To: Zhang, Eniac
> Cc: xen-devel@xxxxxxxxxxxxx
> Subject: RE: [Xen-devel] q35 in xen? vfio in xen?
> 
> 
> On Feb 21, 2014 4:58 PM, "Zhang, Eniac" <eniac-xw.zhang@xxxxxx> wrote:
> >
> > Hi Konrad,
> >
> > Thanks for your reply.
> >
> > Yes, I am aware of the pciback.  Unfortunately it doesn't seem to 
> > support pci-e passthrough. (I could be wrong here)
> 
> I just did PCIe pass through of an VF of an SR-IOV device. It certainly is 
> PCIe.
> 
> >
> > There are two reason that I am interested in this.  For one, my project 
> > calls for pci-e device passthrough, which can't be accomplished with 440fx 
> > chipset emulation.  Secondly, I feel we ought to move on with the 
> > technology.  440fx is ancient in computer terms.  Qemu is good and all 
> > that, but if it refuses to support pci-e natively then it's just a matter 
> > of time that it will become obsoleted.  The trend is clear that pci-e is 
> > taking over the world. 
> >
> 
> I am not sure what you are saying but it does not matter whether QEMU 
> emulates 440fx or q35 for PCI pass through .
> 
> > Regards/Eniac
> >
> > -----Original Message-----
> > From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> > Sent: Friday, February 21, 2014 2:50 PM
> > To: Zhang, Eniac
> > Cc: xen-devel@xxxxxxxxxxxxx
> > Subject: Re: [Xen-devel] q35 in xen? vfio in xen? 
> >
> > On Fri, Feb 21, 2014 at 09:41:39PM +0000, Zhang, Eniac wrote: 
> > > Hi all,
> > > 
> > > I am playing with q35 chipset in qemu (1.6.1).  It seems we can't enable 
> > > q35 machine under xen yet.  I made a few quick hacks which all fail 
> > > miserably (linux kernel oops and window BSOD).  I was wondering why this 
> > > hasn't been done (q35 was introduced into qemu in 2009). 
> > > 
> > > Next question, vfio works very well for me in standalone qemu (with Linux 
> > > host handling iommu), but is that supported under xen?  I haven't tried 
> > > anything there yet because my gut-feeling is that it won't work.  Because 
> > > passing vfio device to qemu can only be done on qemu commandline, and xen 
> > > is not aware of this passing through device, thus not able to make iommu 
> > > arrangement for this device.  Am I on the right track here? 
> >
> > Yes and no. VFIO won't work - but QEMU does do PCI passthrough under Xen. 
> > It uses a different mechanism (and you need to bind the device to pciback). 
> >
> > > 
> > > I am interested in implementing both these two features.  I'd like to 
> > > connect with anyone who's already on this so we don't duplicate the 
> > > efforts. 
> >
> > What do you need Q35 for? 
> >
> > > 
> > > Regards/Eniac
> >
> > > _______________________________________________
> > > Xen-devel mailing list
> > > Xen-devel@xxxxxxxxxxxxx
> > > http://lists.xen.org/xen-devel
> >

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