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Re: [Xen-users] Re: [Xen-devel] pci-passthrough in pvops causing offline raid

On 11/11/2010 11:53 AM, Konrad Rzeszutek Wilk wrote:
On Thu, Nov 11, 2010 at 10:24:17AM +0000, Mark Adams wrote:
Hi All,

Running xen 4.0.1-rc6, debian squeeze 2.6.32-21.

In a voip setup, where I have forwarded the onboard NIC interfaces
through to domU using the following grub config:

module  /vmlinuz-2.6.32-5-xen-amd64 placeholder 
root=UUID=25c3ac79-6850-498d-afcf-ea42970e94fd ro  quiet xen-pciback.permissive 
xen-pciback.hide=(02:00.0)(03:00.0) pci=resource_alignment=02:00.0;03:00.0

I'm having a serious issue where the raid card goes offline after an
indefinate period of time. Sometimes runs fine for a week, other times 1
day before I get "offline device" errors. Rebooting the machine fixes it
straight away, and everything is back online.

What in the Xen pciback is causing the raid card to go offline? The
only devices hidden are the 2 onboard NIC's.
You need to give more details. Is the RAID card a 3Ware? An LSI? Do you
run with an IOMMU? When the RAID card goes offline, do you see a stop of
IRQs going to the device? Are the IRQs for the RAID card sent to all of your
CPUs or just a specific one? Are you pinning your guests to specific CPUs?
Does the issue disappear if you don't passthrough the NIC interfaces? If so have
you run this setup for "a week" to make sure?
I know that this issue is with Xen, as I had this running on a different
server (same xen setup) and it had the same issues, which I initially
thought were to do with the raid card.
So you never ran this setup on this kernel (2.6.32-5) without the Xen 

Is there known issues in this kernel and xen version with pciback? I'm
No. It all works perfectly :-)

going to update to the current package versions this evening (4.0.1-1
and 2.6.32-27) however would appreciate if anyone has any other insight
into this issue, or even just a note to say it is a bug that has been
fixed in current versions!
Well, there were issues with the LSI cards having a hidden PCI device. But those
are pretty obvious as you can't even use it correctly. There is also
a problem with 3Ware 9506 IDE card - which on my box stops sending IRQs
on the IOAPIC it has been assigned (28) and instead uses another one (17).
Not sure if this is just the PCI card using the wrong PCI interrupt pin on the
card and it ends up poking the wrong IOAPIC.

Note: I have no idea if this would be related to your issue or that my assessment is completely accurate.

I had an issue that I feel the debian squeeze kernel running under domU played a part in. My dom0 is Xenified w/Andrew lyon's patches and I running Xen 4.0.2-pre (xen testing). I passthrough a pci tuner card but have not considered that this could also contribute.

Sometimes when I shutdown the domU and upon halt I started getting libata style DRIVE_NOT_READY errors in my dom0. Either one drive would drop from my mdadm raid (which houses my lvm filesystems including root for dom0 and domU) or perhaps they would drop and cause a panic. A reboot fixes everything though a rebuild would occur. I was not able to capture those errors in the few times it happened, but I have since changed to use a 2.6.31 pvops kernel from jeremy's stable branch in my domU and I have yet to reproduce the issue. I did note that it might take a number of days for the problem to manifest and so far I've tested a domU shutdown after 24 and 72 hours using the new kernel with no issues. My next test is @ 7 days.

I wish I had more information myself, but I don't. Regardless of the accuracy of this claim, I recommend trying other kernels to see if the problem persists.

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