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

[Tom Rotenberg <tom.rotenberg@xxxxxxxxx>]

Well, you are correct... however, the situation is that the bgefore
the disable the intx bit was turned off, and only after disable and
then re-enable it was turned on, and that's the strange part of it...

On Wed, Nov 25, 2009 at 11:38 AM, Jiang, Yunhong
<yunhong.jiang@xxxxxxxxx> wrote:
> If the msi_translate=0, why IntX bit is turned on is wrong? I assume guest 
> should use intX in such situation.
>
> --jyh
> ________________________________________
> From: Tom Rotenberg [tom.rotenberg@xxxxxxxxx]
> Sent: Wednesday, November 25, 2009 2:29 AM
> To: Jiang, Yunhong
> Cc: Kamala Narasimhan; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Bug when disabling/enabling a PT device with MSI     
>   enabled
>
> Well, to try and see if the problem is msi related or not, i
> registered the device with the option of 'msi_translate=0' to force
> the use of intx instead of MSI, and i still got the problem... so i
> guess it's not related to the MSI.
>
> It looks like the IntX bit (bit 3 of status word) is runed on somehow
> outside qemu, and that's the problem... could that be?
>
> On Wed, Nov 25, 2009 at 11:17 AM, Jiang, Yunhong
> <yunhong.jiang@xxxxxxxxx> wrote:
>> Sorry send out the mail too quickly.
>> I realized it is MSI translation when I finished first section but forgot 
>> remove it, so please ignore  first section.
>> You only need care about MSI translation, the code is in hw/pass-through.c. 
>>  You can check qemu's changelog at a8d1bd66.
>>
>> --jyh
>> ________________________________________
>> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
>> [xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Jiang, Yunhong 
>> [yunhong.jiang@xxxxxxxxx]
>> Sent: Wednesday, November 25, 2009 2:10 AM
>> To: Tom Rotenberg; Kamala Narasimhan
>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
>> Subject: RE: [Xen-devel] Bug when disabling/enabling a PT device with MSI   
>>     enabled
>>
>> This should be about qemu's MSI support. The code is in qemu/hw/pt-msi.c for 
>> all MSI emulation.
>> Windows XP does not support MSI if I remember correctly. SO this issue 
>> should be about MSI translation, i.e. guest is using IOAPIC while host is 
>> using MSI. Xen hypervisor will translate the MSI to guest's IOAPIC.
>>
>> --jyh
>> ________________________________________
>> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
>> [xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Tom Rotenberg 
>> [tom.rotenberg@xxxxxxxxx]
>> Sent: Wednesday, November 25, 2009 1:27 AM
>> To: Kamala Narasimhan
>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
>> Subject: Re: [Xen-devel] Bug when disabling/enabling a PT device with MSI   
>>     enabled
>>
>> 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
>>>>
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>>> http://lists.xensource.com/xen-devel
>>>
>>
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>

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