Re: [Xci-devel] Porblem with disabling and then re-enabling a PT device in Windows

[Tom Rotenberg <tom.rotenberg@xxxxxxxxx>]

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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