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RE: [Xen-devel] Re: [Xci-devel] Porblem with disabling and then re-enabl

To: Tom Rotenberg <tom.rotenberg@xxxxxxxxx>, Kamala Narasimhan <Kamala.Narasimhan@xxxxxxxxxx>
Subject: RE: [Xen-devel] Re: [Xci-devel] Porblem with disabling and then re-enabling a PT device in Windows
From: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
Date: Thu, 26 Nov 2009 09:40:25 +0800
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Thread-topic: [Xen-devel] Re: [Xci-devel] Porblem with disabling and then re-enabling a PT device in Windows

xen-devel-bounces@xxxxxxxxxxxxxxxxxxx wrote:
> After digging more into this problem, i found out that the problem is
> because the interrupt generated on the wlan device, isn't being
> transfered to the domain, for some reason, after the device was
> re-enablked in Windows. I saw that, by connecting to the xen console,
> and then clicking 'i', and i got the following lines:
> ...
> (XEN)    Vec192 IRQ 17: type=IO-APIC-level   status=00000010
> in-flight=1 domain-list=0: 17(----),3: 17(---M),
> ...
> (XEN)       Apic 0x00, Pin 17: vector=192, delivery_mode=1,
> dest_mode=logical, delivery_status=1, polarity=1, irr=1,
> trigger=level, mask=0 ....
> You can see, that the interrupt 17, which is in my Windows domU, was
> generated, but still weren't injected to the CPU (the 'irr' is 1). So,
> i guess that this is what is causing the problem.
> Now, the only issue left, is why the hell, the interrupt isn't being
> injected to the domain? 

I assume you are using ack_type_new on your system, am I right?
Usually it means guest has not EOI the interrupt, so that host has no chance to 
EOI the physical IOAPIC. Can you check the virtual Local APIC/IOAPIC for the 
guest to see if we have any finding?
BTW, does it happen everytime?


> Has anyone has any idea about it?
> On Wed, Nov 25, 2009 at 6:31 PM, Tom Rotenberg
> <tom.rotenberg@xxxxxxxxx> wrote:
>> Well, i just performed some tests, and it doesn't look like the
>> disable_msi/enable_msi functions in pciback are being called at all
>> (moreover, not in the disable-enable from domU Windows XP), so i
>> don't think it's related. Also, since when, a config space write
>> from a guest domU triggers code in the pciback? 
>> I think that it's not the problem here...
>> Maybe someone from the XCI can shed some light here, and tell us how
>> they solve it (or not)? since their code should run on the same Dell
>> machines, no? 
>> On Wed, Nov 25, 2009 at 5:13 PM, Kamala Narasimhan
>> <Kamala.Narasimhan@xxxxxxxxxx> wrote:
>>> I shouldn't have suggested that you build without pciback;
> I got carried away trying to make it simple for you :-);
> Obviously you would need it and I should have stopped with
> suggesting that you tweak it.
>>> Here is the thought process that led to my suggestion -
>>> Clearly, that bit is getting changed as indicated in your
> log.  It is unlikely that the guest is triggering that change
> which makes pciback a potential candidate to suspect as it
> does change pci configuration space bits.  I need to add some
> tracing and look at the path of execution to answer some of
> your specific questions accurately and I won't be able to do
> that right now but I can give some context to help you based
> on what I have experienced in comparable situation and based
> on that I would say pciback is one place to suspect.  To be a
> bit more specific I would say look into
> pciback_enable_msi/pciback_disable_msi code, add some tracing
> there, observe whether or not that code path is taken when the
> device is disabled/reenabled within guest etc.  To reiterate,
> these are mere suggestions but looks plausible based on prior
> observations.
>>> Kamala
>>>> -----Original Message-----
>>>> From: Tom Rotenberg [mailto:tom.rotenberg@xxxxxxxxx]
>>>> Sent: Wednesday, November 25, 2009 9:22 AM
>>>> To: Kamala Narasimhan
>>>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; xci-devel@xxxxxxxxxxxxxxxxxxx
>>>> Subject: Re: [Xci-devel] Porblem with disabling and then
>>>> re-enabling a PT device in Windows 
>>>> I am not sure i undertand how to test it...
>>>> 1) Avoid doing FLR for the device - isn';t that done only when
>>>> building the domain? does that happen when i disable the device in
>>>> domU? 2) Don't build pciback - and then, i won't bind the wlan
>>>> device to pciback? and change the xend scripts which check for it?
>>>> 3) Comment out the relevant code - which code??
>>>> I also don't understand, how could it be that the pciback device is
>>>> "messing" with it? isn't it supposed to be in-active when the
>>>> device is being used in PT? 
>>>> Tom
>>>> On Wed, Nov 25, 2009 at 4:12 PM, Kamala Narasimhan
>>>> <Kamala.Narasimhan@xxxxxxxxxx> wrote:
>>>>> There is a chance pciback is changing the bit you are referring
>>>> to.  To confirm that, just for testing purpose you might want to
>>>> avoid FLR for that device or simply not build pciback or comment
>>>> out relevant code in that module whichever is easier and see if
>>>> that helps.  If it does, you can then look into fixing the problem
>>>> the right way. 
>>>>> Kamala
>>>>>> -----Original Message-----
>>>>>> From: xci-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xci-devel-
>>>>>> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Tom Rotenberg
>>>>>> Sent: Wednesday, November 25, 2009 8:09 AM
>>>>>> To: xen-devel@xxxxxxxxxxxxxxxxxxx; xci-devel@xxxxxxxxxxxxxxxxxxx
>>>>>> Subject: [Xci-devel] Porblem with disabling and then re-enabling
>>>>>> a PT device in Windows 
>>>>>> Hi All,
>>>>>> (This is a continuation to my previous mail, but since it looks
>>>>>> like a different problem - i decided to open a new thread for it)
>>>>>> ----
>>>>>> Problem Description:
>>>>>> ----
>>>>>> I am doing pass-through of an Intel wireless LAN device to a
>>>>>> Windows XP domU (my machine is Dell e6400), and it looks like
>>>>>> it's working ok. Then, i disable the device using Windows device
>>>>>> manager, and the device is now disabled, after that i re-enable
>>>>>> the device, and Windows re-enables the device correctly.
>>>>>> However, the wlan device seems to malfunction (it can't turn on
>>>>>> the WiFi of the computer), and can't connect to wireless
>>>>>> networks. I tried it, both with MSI translation on, and with MSI
>>>>>> translation off - it doesn't matter.  
>>>>>> ----
>>>>>> My analysis:
>>>>>> ----
>>>>>> 1) Well, taking a look at the real PCI config space, before
>>>>>> disable and after the (last) enable, shows that the difference
>>>>>> is at the Intx bit (read-only bit 3 at status register (offset
>>>>>> 0x6) at the PCI config space). Before disable, that bit was 0,
>>>>>> and after the last enable that bit was 1. This, according to my
>>>>>> understanding, means that the device is asserting it's IntX ,
>>>>>> and probably waiting for someone to handle it, no? 
>>>>>> 2) When i tried to track when did this bit was changed - i added
>>>>>> a code which in every PCI config read, checks if that bit was
>>>>>> changed - and added a print when it changed. The proper lines in
>>>>>> the qemu log looks like this: ...
>>>>>> pt_pci_read_config: [00:01.0]: address=00f0 val=0x00000000 len=2
>>>>>> ACPI PCI hotplug: read addr=0x10c6, val=0x0f.
>>>>>> ACPI PCI hotplug: read addr=0x10c6, val=0x0f.
>>>>>> pt_pci_read_config: TEST CODE: STATUS CHNAGED! OLD: 0x10, NEW:
>>>>>> 0x18 pt_pci_read_config: [00:01.0]: address=0000 val=0x00008086
>>>>>> len=2 ... 
>>>>>> This implies that the bit was changed, about the same time that
>>>>>> Windows tried to start using it (because, i assume that it tried
>>>>>> using it, just after questioning the ACPI for the existence of
>>>>>> the device). No? 
>>>>>> Can someone help me with this?
>>>>>> (BTW - i am using Xen 3.4)
>>>>>> Tom
>>>>>> _______________________________________________
>>>>>> Xci-devel mailing list
>>>>>> Xci-devel@xxxxxxxxxxxxxxxxxxx
>>>>>> http://lists.xensource.com/mailman/listinfo/xci-devel
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