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Re: [Xen-devel] libxl: problem with devices in PV

To: Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] libxl: problem with devices in PV
From: Roger Pau Monné <roger.pau@xxxxxxxxxxxxx>
Date: Thu, 21 Jul 2011 11:19:56 +0200
Cc: Christoph Egger <Christoph.Egger@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Stefano@xxxxxxxxxx" <Stefano@xxxxxxxxxx>, Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>
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2011/7/21 Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>:
> On Thu, 2011-07-21 at 09:39 +0100, Roger Pau Monné wrote:
>> Hello,
>> Thanks for the help, I have a preliminary patch that allows booting PV
>> machines with xl on NetBSD, but there seems to be some issues with PCI
>> devices, the guest takes a very long time to start, and I think it's
>> because it's waiting for PCI devices to initialize.
>> [    5.280068] XENBUS: Waiting for devices to initialise:
>> 295s...290s...285s...280s...275s...270s...265s...260s...255s...250s...245s...240s...235s...230s...225s...220s...215s...210s...205s...200s...195s...190s...185s...180s...175s...170s...165s...160s...155s...150s...145s...140s...135s...130s...125s...120s...115s...110s...105s...100s...95s...90s...85s...80s...75s...70s...65s...60s...55s...50s...45s...40s...35s...30s...25s...20s...15s...10s...5s...0s...
>> [  300.280078] XENBUS: Device with no driver: device/vbd/51714
>> [  300.280086] XENBUS: Device with no driver: device/vbd/51713
>> [  300.280495] XENBUS: Timeout connecting to device: device/pci/0
>> (local state 3, remote state 1)
>> xm didn't add pci entries to xenstore, and I don't know what should be
>> the status of those entries, or if it's best to disable the adding of
>> pci entries to xenstore in libxl if no devices are configured?
>> I've looked at http://wiki.xensource.com/xenwiki/XenStoreReference,
>> but the wiki doesn't have any information regarding PCI xenstore
>> entries.
>> The status of those entries in xenstore is the following:
>> /local/domain/0/backend/pci = ""   (n0)
>> /local/domain/0/backend/pci/1 = ""   (n0)
>> /local/domain/0/backend/pci/1/0 = ""   (n0,r1)
>> /local/domain/0/backend/pci/1/0/frontend =
>> "/local/domain/1/device/pci/0"   (n0,r1)
>> /local/domain/0/backend/pci/1/0/frontend-id = "1"   (n0,r1)
>> /local/domain/0/backend/pci/1/0/online = "1"   (n0,r1)
>> /local/domain/0/backend/pci/1/0/state = "1"   (n0,r1)
>> /local/domain/0/backend/pci/1/0/domain = "debian"   (n0,r1)
>> /local/domain/0/backend/pci/1/0/num_devs = "0"   (n0,r1)
> num_devs = 0, is it the case that you don't actually have any pci
> devices in your configuration?

No, I didn't have any PCI devices set.

> I wonder if perhaps the netbsd pciback doesn't like seeing a backend
> directory with no actual devices in it.
> Could you try experimentally commenting out the call to
> libxl__create_pci_backend in do_domain_create, or gating it on "if
> (d_config->num_pcidevs)".

Disabling or setting it with a if condition makes the guest boot, I
through that setting the appropriate values in the status of xenstore
should also work, but it's useless to have references to PCI devices
in xenstore if no devices are actually configured.

> That call was added in 23565:72eafe80ebc1 but I don't think adding the
> if would invalidate it.
>> /local/domain/1/device/pci = ""   (n0,r1)
>> /local/domain/1/device/pci/0 = ""   (n1,r0)
>> /local/domain/1/device/pci/0/backend =
>> "/local/domain/0/backend/pci/1/0"   (n1,r0)
>> /local/domain/1/device/pci/0/backend-id = "0"   (n1,r0)
>> /local/domain/1/device/pci/0/state = "3"   (n1,r0)
>> /local/domain/1/device/pci/0/pci-op-ref = "8"   (n1,r0)
>> /local/domain/1/device/pci/0/event-channel = "8"   (n1,r0)
>> /local/domain/1/device/pci/0/magic = "7"   (n1,r0)
>> The patch attached breaks linux support, it is only attached for
>> informative purposes.
>> Regards, Roger.

Thanks again for all the help, I would prepare a new proper patch to
be added to mainline Xen.

Regards, Roger.

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