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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