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!!!

From: Boris Ostrovsky
Date: Fri May 22 2015 - 21:54:11 EST

On 05/22/2015 04:11 AM, Sander Eikelenboom wrote:
Hello Sander,

Friday, May 15, 2015, 12:47:27 AM, you wrote:

Sorry for the resend, i messed up the to's en from's.

Hi Konrad / David,

One big snip on this thread, got some more debug info, hopefully this will
lead to something:

On a working kernel (with the two seemingly non related patches reverted) i get:

[ 0.717796] pcifront pci-0: Allocated pdev @ 0xffff880019e11780 pdev->sh_info @ 0xffff880018f58000
[ 0.717848] pcifront pci-0: ?!?!? before alloc gntref: 0
[ 0.717871] pcifront pci-0: ?!?!? after alloc gntref: 8
[ 0.717892] pcifront pci-0: ?!?!? before alloc evtchn: -1
[ 0.717915] pcifront pci-0: ?!?!? after alloc evtchn: 17
[ 0.717984] pcifront pci-0: ?!?!? bound evtchn:17 to irqhandler:-1 err:31
[ 0.721640] pcifront pci-0: publishing successful!
[ 0.723684] usbcore: registered new interface driver udlfb
[ 0.724664] xen:xen_evtchn: Event-channel device installed
[ 0.726597] pcifront pci-0: Installing PCI frontend
[ 0.726853] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
[ 0.727059] pcifront pci-0: Creating PCI Frontend Bus 0000:00
[ 0.727363] pcifront pci-0: PCI host bridge to bus 0000:00
[ 0.727391] pci_bus 0000:00: root bus resource [io 0x0000-0xffff]
[ 0.727417] pci_bus 0000:00: root bus resource [mem 0x00000000-0xffffffffffff]
[ 0.727452] pci_bus 0000:00: root bus resource [bus 00-ff]
[ 0.727475] pci_bus 0000:00: scanning bus
[ 0.727503] pcifront pci-0: read dev=0000:00:00.0 - offset 0 size 4
[ 0.728253] Linux agpgart interface v0.103
[ 0.728387] Hangcheck: starting hangcheck timer 0.9.1 (tick is 180 seconds, margin is 60 seconds).
[ 0.728474] [drm] Initialized drm 1.1.0 20060810
[ 0.728551] [drm] radeon kernel modesetting enabled.
[ 0.730319] pcifront pci-0: ?!?!? pciback responded !!! irq:31 irq_flags:ffff880019e100a8 ns: 1431641785551700000 ns_timeout: 1431641787541235000 evtchn:17 gnt_ref:8
[ 0.730319] pcifront pci-0: ?!?!? op cmd:0 err:0 info:0 offset:0 size:4
[ 0.730319] pcifront pci-0: ?!?!? active_op cmd:0 err:0 info:0 offset:0 size:4
[ 0.730319] pcifront pci-0: read got back value 11113f6
[ 0.738845] pcifront pci-0: read dev=0000:00:00.0 - offset e size 1
[ 0.744976] brd: module loaded
[ 0.745204] pcifront pci-0: ?!?!? pciback responded !!! irq:31 irq_flags:ffff880019e100a8 ns: 1431641785562852000 ns_timeout: 1431641787552580000 evtchn:17 gnt_ref:8
[ 0.745204] pcifront pci-0: ?!?!? op cmd:0 err:0 info:0 offset:14 size:1
[ 0.745204] pcifront pci-0: ?!?!? active_op cmd:0 err:0 info:0 offset:14 size:1
[ 0.745204] pcifront pci-0: read got back value 0
[ 0.749204] pcifront pci-0: read dev=0000:00:00.0 - offset 6 size 2
[ 0.750155] loop: module loaded
[ 0.752527] pcifront pci-0: ?!?!? pciback responded !!! irq:31 irq_flags:ffff880019e100a8 ns: 1431641785570841000 ns_timeout: 1431641787562917000 evtchn:17 gnt_ref:8
[ 0.752527] pcifront pci-0: ?!?!? op cmd:0 err:0 info:0 offset:6 size:2
[ 0.752527] pcifront pci-0: ?!?!? active_op cmd:0 err:0 info:0 offset:6 size:2
[ 0.752527] pcifront pci-0: read got back value 210
[ 0.757187] pcifront pci-0: read dev=0000:00:00.0 - offset 34 size 1


Were as in the non-working situation i get:

[ 0.751244] pcifront pci-0: Allocated pdev @ 0xffff880019ec2e00 pdev->sh_info @ 0xffff88001aa51000
[ 0.751295] pcifront pci-0: ?!?!? before alloc gntref: 0
[ 0.751315] pcifront pci-0: ?!?!? after alloc gntref: 8
[ 0.751334] pcifront pci-0: ?!?!? before alloc evtchn: -1
[ 0.751355] pcifront pci-0: ?!?!? after alloc evtchn: 17
[ 0.751422] pcifront pci-0: ?!?!? bound evtchn:17 to irqhandler:-1 err:31
[ 0.755215] pcifront pci-0: publishing successful!
[ 0.757341] usbcore: registered new interface driver udlfb
[ 0.758365] xen:xen_evtchn: Event-channel device installed
[ 0.760419] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
[ 0.760819] pcifront pci-0: Installing PCI frontend
[ 0.761518] pcifront pci-0: Creating PCI Frontend Bus 0000:00
[ 0.761684] pcifront pci-0: PCI host bridge to bus 0000:00
[ 0.761710] pci_bus 0000:00: root bus resource [io 0x0000-0xffff]
[ 0.761733] pci_bus 0000:00: root bus resource [mem 0x00000000-0xffffffffffff]
[ 0.761763] pci_bus 0000:00: root bus resource [bus 00-ff]
[ 0.761783] pci_bus 0000:00: scanning bus
[ 0.761805] pcifront pci-0: read dev=0000:00:00.0 - offset 0 size 4
[ 0.767207] Linux agpgart interface v0.103
[ 0.767362] Hangcheck: starting hangcheck timer 0.9.1 (tick is 180 seconds, margin is 60 seconds).
[ 0.767439] [drm] Initialized drm 1.1.0 20060810
[ 0.767515] [drm] radeon kernel modesetting enabled.
[ 0.766948] pcifront pci-0: pciback not responding!!! irq:31 irq_flags:ffff880019ec0028 ns: 1431641983026498000 ns_timeout: 1431641983026497000 evtchn:0 gnt_ref:0
[ 0.766948] pcifront pci-0: ?!?!? op cmd:0 err:0 info:0 offset:0 size:4
[ 0.766948] pcifront pci-0: ?!?!? active_op cmd:0 err:0 info:0 offset:0 size:4
[ 0.766948] pcifront pci-0: other err read got back err: ffffffff value: 0
[ 2.762062] pcifront pci-0: read dev=0000:00:01.0 - offset 0 size 4
[ 2.765203] pcifront pci-0: pciback not responding!!! irq:31 irq_flags:ffff880019ec0028 ns: 1431641985026742000 ns_timeout: 1431641985026741000 evtchn:0 gnt_ref:0
[ 2.765203] pcifront pci-0: ?!?!? op cmd:0 err:0 info:0 offset:0 size:4
[ 2.765203] pcifront pci-0: ?!?!? active_op cmd:0 err:0 info:0 offset:0 size:4
[ 2.765203] pcifront pci-0: other err read got back err: ffffffff value: 0
[ 4.762172] pcifront pci-0: read dev=0000:00:02.0 - offset 0 size 4
[ 4.764231] brd: module loaded
[ 4.765508] loop: module loaded
[ 4.766748] pcifront pci-0: pciback not responding!!! irq:31 irq_flags:ffff880019ec0028 ns: 1431641987026850000 ns_timeout: 1431641987026849000 evtchn:0 gnt_ref:0
[ 4.766748] pcifront pci-0: ?!?!? op cmd:0 err:0 info:0 offset:0 size:4
[ 4.766748] pcifront pci-0: ?!?!? active_op cmd:0 err:0 info:0 offset:0 size:4
[ 4.766748] pcifront pci-0: other err read got back err: ffffffff value: 0
[ 6.762248] pcifront pci-0: read dev=0000:00:03.0 - offset 0 size 4
[ 6.765545] pcifront pci-0: pciback not responding!!! irq:31 irq_flags:ffff880019ec0028 ns: 1431641989026930000 ns_timeout: 1431641989026929000 evtchn:0 gnt_ref:0
[ 6.765545] pcifront pci-0: ?!?!? op cmd:0 err:0 info:0 offset:0 size:4
[ 6.765545] pcifront pci-0: ?!?!? active_op cmd:0 err:0 info:0 offset:0 size:4
[ 6.765545] pcifront pci-0: other err read got back err: ffffffff value: 0
[ 8.762329] pcifront pci-0: read dev=0000:00:04.0 - offset 0 size 4
[ 8.765626] pcifront pci-0: pciback not responding!!! irq:31 irq_flags:ffff880019ec0028 ns: 1431641991027006000 ns_timeout: 1431641991027005000 evtchn:0 gnt_ref:0
[ 8.765626] pcifront pci-0: ?!?!? op cmd:0 err:0 info:0 offset:0 size:4
[ 8.765626] pcifront pci-0: ?!?!? active_op cmd:0 err:0 info:0 offset:0 size:4
[ 8.765626] pcifront pci-0: other err read got back err: ffffffff value: 0
[ 10.762410] pcifront pci-0: read dev=0000:00:05.0 - offset 0 size 4
[ 10.765701] pcifront pci-0: pciback not responding!!! irq:31 irq_flags:ffff880019ec0028 ns: 1431641993027087000 ns_timeout: 1431641993027086000 evtchn:0 gnt_ref:0
[ 10.765701] pcifront pci-0: ?!?!? op cmd:0 err:0 info:0 offset:0 size:4
[ 10.765701] pcifront pci-0: ?!?!? active_op cmd:0 err:0 info:0 offset:0 size:4
[ 10.765701] pcifront pci-0: other err read got back err: ffffffff value: 0
[ 12.762472] pcifront pci-0: read dev=0000:00:06.0 - offset 0 size 4


So somehow in the non-working situation, pdev->evtchn and pdev->gnt_ref are 0 in
xen-pcifront.c:do_pci_op(), so no wonder it's not getting a response back ...

Question is .. why ?

--
Sander


Ping ?

David / Boris,

Any idea, since Konrad seems to be off for 2 weeks and we are at rc4 now.


(+Rafael again)

So the immediate cause of those errors is that pdev->evtchn is 0. Backend is not notified and things not go well then.

And it is indeed caused by 97badf873ab60e841243b66133ff9eff2a46ef29:

We allocate pcifront_sd in pcifront_scan_root() and then pass it to pci_scan_bus_parented() as sysdata. Eventually this sysdata is used in pcibios_root_bridge_prepare() as pci_sysdata. It is dereferenced as pci_sysdata->companion (which I believe is aliased to pcifront_sd->pdev) and then set_primary_fwnode() writes it, thus corrupting pcifront_sd->pdev (and I think this is what sets evtchn to zero).

I don't have a fix for that. I will see what we can do on Tuesday since I am out on Monday.

Question to Rafael about commit 97badf873ab60e84124: is it really safe to assume that bridge->bus->sysdata is a pointer to pci_sysdata in pcibios_root_bridge_prepare()? It is declared as 'void *'.

-boris


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