Re: FreeBSD guest with VTD NIC not passing traffic

[Jan Kiszka <jan.kiszka@web.de>]

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On 2012-01-04 04:21, Alex Williamson wrote:
> On Mon, 2011-12-19 at 19:49 +0530, Shashidhar Patil wrote:
>> Hi,
>>        I am running Ubuntu 10.10 (amd64) on a 2 socket  nehalem based
>> server with IOH 5520. 5520 supports VTD.
>> I enabled DMAR with intel_iommu=on. The box has intel 82599 adapter
>> which I assigned through VT-D to FreeBSD 8.2 running
>> as guest os. The ixgbe driver detects the device and the driver
>> successfully configures the device. But the link
>> never comes up. It looks like link up/down interrupts are not
>> delivered. Then I checked kvm interrupt assignment and as expected
>> kvm could not make MSI-X entries for the VT-d guest. So no output from
>> "grep kvm /proc/interrupt". By enabling some debugs in the
>> qemu-kvm I figured out that the MSI-x updates are not received
>> properly. It does look like Linux updates MSI-X table in a batch
>> fashion
>> which qemu-kvm gets in  one shot and every thing works fine in case of
>> linux. In case of FreeBSD PCIE updates come /MSI-X entry
>> which qemu-kvm can't make use.
> 
> That's right, Linux and Windows both seem to setup the MSI-X table then
> enable it in one shot, so we only trigger the interrupt programming when
> the enable bit is set.  We don't trigger changes on writes to the MSI-X
> table... not very accurate emulation of mask bits.

According to the PCI spec, updates that happen while a vector is
unmasked, need not be considered by the hardware (thus the hypervisor
here). Is that the scenario here?

Jan


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