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Re: [Xen-devel] Bug when disabling/enabling a PT device with MSI enable

To: Kamala Narasimhan <Kamala.Narasimhan@xxxxxxxxxx>
Subject: Re: [Xen-devel] Bug when disabling/enabling a PT device with MSI enabled
From: Tom Rotenberg <tom.rotenberg@xxxxxxxxx>
Date: Wed, 25 Nov 2009 10:27:11 +0200
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Well, just tested it with the 2.6.18 latest kernel, and the bug still exists.
Also, i think that iit's more related to how qemu handles the
"disable/enable" of domU for PT devices with MSI... but i don't know
where to start from? it looks like when re-enabling a PT device with
MSI, we need qemu to re-initialize the device according to it's
original MSI state (and not to what it was resetted before).

Does anyone has any clue about it?

On Wed, Nov 25, 2009 at 4:25 AM, Kamala Narasimhan
<Kamala.Narasimhan@xxxxxxxxxx> wrote:
> Couple of questions -
> 1) What kind of device are you referring to below?  Display by any chance?
> 2) Which tree is your dom0 kernel based on?
> There is a chance you are missing some msi patches in your dom0 kernel.  You 
> might want to do a quick search for msi patches in 
> http://xenbits.xen.org/staging/linux-2.6.18-xen.hg?rev=msi and see if you are 
> missing anything obvious.  I recently encountered a similar issue in a 
> slightly different situation, a subset of the problem was caused because of 
> missing msi patches.
> Kamala
>> -----Original Message-----
>> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
>> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Tom Rotenberg
>> Sent: Tuesday, November 24, 2009 1:43 PM
>> To: xen-devel@xxxxxxxxxxxxxxxxxxx
>> Subject: [Xen-devel] Bug when disabling/enabling a PT device with MSI
>> enabled
>> Hi,
>> I am using the xen-3,4, and i am doing pass-through for a device with
>> MSI enabled (the device of-course supports MSI) to a domU with Windows
>> XP. When i disable and then re-enable the device using Windows device
>> manager, everything looks like it's working fine, but the device seems
>> to malfunction.
>> After digging a little bit, i saw that the problem is, because the bit
>> of the interrupt-status (bit 3) in the status register (offset 0x6 in
>> the PCI config space) was turned on somehow -  this proibably caused
>> the MSI to malfunction (because the IntX assertion was enabled - thus
>> disabling the MSI) - and this lead to the problem i experienced.
>> Any ideas on how to solve this issue?
>> Tom
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