Re: [Xen-devel] Regression due to "device property: Make it possible to use secondary firmware nodes" Re: Xen-unstable + linux 4.1-mergewindow: problems with PV guest pci passthrough: pcifront pci-0: pciback not responding!!!

["Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>]

On Wednesday, May 13, 2015 12:52:36 AM Sander Eikelenboom wrote:
> 
> Tuesday, May 12, 2015, 5:45:06 PM, you wrote:
> 
> > On Tuesday, May 12, 2015 02:59:57 AM Rafael J. Wysocki wrote:
> >> On Monday, May 11, 2015 11:20:29 AM Konrad Rzeszutek Wilk wrote:
> >> > On Tue, May 05, 2015 at 12:18:49AM +0200, Sander Eikelenboom wrote:
> >> > > Hello Sander,
> >> > > 
> >> > > Monday, April 27, 2015, 5:48:00 PM, you wrote:
> >> > > 
> >> > > > Hi David / Konrad,
> >> > > 
> >> > > > Here the other problem i found, which is introduced somewhere in the 
> >> > > > 4.1 mergewindow:
> >> > > 
> >> > > > on 4.1.0-rc1 (with the one revert to get things booting) i get this 
> >> > > > in
> >> > > > the PV Guest console:
> >> > > 
> >> > > > [    0.517392] crc32c_combine: 8373 self tests passed
> >> > > > [    0.517608] pci_hotplug: PCI Hot Plug PCI Core version: 0.5
> >> > > > [    0.517655] pciehp: PCI Express Hot Plug Controller Driver 
> >> > > > version: 0.4
> >> > > > [    0.517677] cpcihp_generic: Generic port I/O CompactPCI Hot Plug 
> >> > > > Driver version: 0.1
> >> > > > [    0.517684] cpcihp_generic: not configured, disabling.
> >> > > > [    0.517700] shpchp: Standard Hot Plug PCI Controller Driver 
> >> > > > version: 0.4
> >> > > > [    0.517713] acpiphp_ibm: ibm_acpiphp_init: acpi_walk_namespace 
> >> > > > failed
> >> > > > [    0.519849] usbcore: registered new interface driver udlfb
> >> > > > [    0.613289] xen:xen_evtchn: Event-channel device installed
> >> > > > [    0.613436] pcifront pci-0: Installing PCI frontend
> >> > > > [    0.613578] pcifront pci-0: Creating PCI Frontend Bus 0000:00
> >> > > > [    0.613616] pcifront pci-0: PCI host bridge to bus 0000:00
> >> > > > [    0.613624] pci_bus 0000:00: root bus resource [io  0x0000-0xffff]
> >> > > > [    0.613631] pci_bus 0000:00: root bus resource [mem 
> >> > > > 0x00000000-0xffffffffffff]
> >> > > > [    0.613638] pci_bus 0000:00: root bus resource [bus 00-ff]
> >> > > > [    0.616672] pcifront pci-0: pciback not responding!!!
> >> > > > [    2.613762] clocksource tsc: mask: 0xffffffffffffffff max_cycles: 
> >> > > > 0x2e20fd6f2ba, max_idle_ns: 440795302556 ns
> >> > > > [    2.614275] Serial: 8250/16550 driver, 4 ports, IRQ sharing 
> >> > > > enabled
> >> > > > [    2.614682] Linux agpgart interface v0.103
> >> > > > [    2.614731] Hangcheck: starting hangcheck timer 0.9.1 (tick is 
> >> > > > 180 seconds, margin is 60 seconds).
> >> > > > [    2.614762] [drm] Initialized drm 1.1.0 20060810
> >> > > > [    2.614789] [drm] radeon kernel modesetting enabled.
> >> > > > [    2.616529] brd: module loaded
> >> > > > [    2.617844] loop: module loaded
> >> > > > [    2.620008] pcifront pci-0: pciback not responding!!!
> >> > > > [    4.621490] pcifront pci-0: pciback not responding!!!
> >> > > > [    6.621866] pcifront pci-0: pciback not responding!!!
> >> > > > [    8.622421] pcifront pci-0: pciback not responding!!!
> >> > > > etc. etc. etc.
> >> > > 
> >> > > 
> >> > > > Where on 4.0.0 it get:
> >> > > 
> >> > > > [    0.442554] shpchp: Standard Hot Plug PCI Controller Driver 
> >> > > > version: 0.4
> >> > > > [    0.442583] acpiphp_ibm: ibm_acpiphp_init: acpi_walk_namespace 
> >> > > > failed
> >> > > > [    0.443293] pcifront pci-0: Allocated pdev @ 0xffff88001ab23c00 
> >> > > > pdev->sh_info @ 0xffff88001937f000
> >> > > > [    0.444885] pcifront pci-0: publishing successful!
> >> > > > [    0.445302] usbcore: registered new interface driver udlfb
> >> > > > [    0.445829] xen:xen_evtchn: Event-channel device installed
> >> > > > [    0.446499] pcifront pci-0: Installing PCI frontend
> >> > > > [    0.446715] pcifront pci-0: Creating PCI Frontend Bus 0000:00
> >> > > > [    0.446951] pcifront pci-0: PCI host bridge to bus 0000:00
> >> > > > [    0.446960] pci_bus 0000:00: root bus resource [io  0x0000-0xffff]
> >> > > > [    0.446968] pci_bus 0000:00: root bus resource [mem 
> >> > > > 0x00000000-0xffffffffffff]
> >> > > > [    0.446988] pci_bus 0000:00: root bus resource [bus 00-ff]
> >> > > > [    0.447002] pci_bus 0000:00: scanning bus
> >> > > > [    0.447140] pci 0000:00:00.0: [13f6:0111] type 00 class 0x040100
> >> > > > [    0.447520] pci 0000:00:00.0: reg 0x10: [io  0x7800-0x78ff]
> >> > > > [    0.449148] pci 0000:00:00.0: supports D1 D2
> >> > > > [    0.449791] pci_bus 0000:00: fixups for bus
> >> > > > [    0.449794] pci_bus 0000:00: bus scan returning with max=00
> >> > > > [    0.450604] Serial: 8250/16550 driver, 4 ports, IRQ sharing 
> >> > > > enabled
> >> > > > [    0.451991] Linux agpgart interface v0.103
> >> > > > [    0.452160] Hangcheck: starting hangcheck timer 0.9.1 (tick is 
> >> > > > 180 seconds, margin is 60 seconds).
> >> > > > [    0.452222] [drm] Initialized drm 1.1.0 20060810
> >> > > > [    0.452300] [drm] radeon kernel modesetting enabled.
> >> > > > [    0.462384] pcifront pci-0: claiming resource 0000:00:00.0/0
> >> > > 
> >> > > > But i thought the patches that would change pci bus scanning were 
> >> > > > destined for 
> >> > > > 4.2 though ...
> >> > > 
> >> > > > --
> >> > > > Sander
> >> > > 
> >> > > Hi David / Konrad,
> >> > > 
> >> > > I have bisected this one .. it leads to:
> >> > > 
> >> > > commit 97badf873ab60e841243b66133ff9eff2a46ef29
> >> > > Author: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >> > > Date:   Fri Apr 3 23:23:37 2015 +0200
> >> > > 
> >> > > device property: Make it possible to use secondary firmware nodes
> >> > > 
> >> > > Since i didn't see it directly related to pci-front, i double checked 
> >> > > by 
> >> > > reverting this commit(and 9b73262ccbf2fb0060303f047863214269e64f9a 
> >> > > since it 
> >> > > build depends on the other) on 4.1-rc2.
> >> > > 
> >> > > Reverting in the guest kernel indeed makes pci-front work correct 
> >> > > again.
> >> > 
> >> > That is quite odd.
> >> 
> >> Yes, that's weird.
> >> 
> >> > And sadly I am due for vacation at the end of this week
> >> > so own't be able to look at this (and prepare an debug patch for the MSI
> >> > addendum debug patch either).
> >> > 
> >> > 
> >> > Rafael,
> >> > 
> >> > Were there any other bug reports about this particular commit?
> >> 
> >> Not that I'm aware of.
> >> 
> >> I'll look at that tomorrow when I'm a bit less tired.
> 
> > So since device_add_property_set() is not currently used, the commit it's
> > been bisected to should not have any functional effects on anything, but
> > nevertheless please apply the appended debug patch and see if you get any
> > extra output from it.
> 
> > That said, the commit might make a difference for Xen if there's an already
> > existing initialization ordering issue, because it slows down the ACPI/PCI
> > initialization a bit (due to the new checks in set_primary_fwnode()) and
> > something already racy with respect to it may be able to win the race now.
> 
> > So I'm wondering, for example, if adding something like msleep(100); at the
> > beginning of pcifront_init() (right after the initial checks) will make any
> > difference.
> 
> Hi Rafael,
> 
> The WARN's don't trigger, so it's a red herring i suppose :-(

It seems so.

The commit also changes the size of struct acpi_device, but that shouldn't
matter.

> I also tried the msleep(100), but that didn't change anything as well. 

I see.

Well, I'm not really familiar with the Xen-related code, so it is hard to
me to give you any useful advice here.


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

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