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Date:	Mon, 14 Jul 2014 13:22:25 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Sander Eikelenboom <linux@...elenboom.it>
Cc:	konrad@...nel.org, xen-devel@...ts.xenproject.org,
	boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
	linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH v4] PCI back fixes for 3.17.

On Mon, Jul 14, 2014 at 06:37:55PM +0200, Sander Eikelenboom wrote:
> 
> Friday, July 11, 2014, 10:08:47 PM, you wrote:
> 
> > Please see this set of patches which are fixes to Xen pciback
> > for 3.17. They are also located at:
> 
> >  git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git devel/pciback-3.17.v4 
> 
> > These patches do not include the PCI bus reset/slot code as we are still
> > discussing that.
> 
> > Konrad Rzeszutek Wilk (5):
> >       xen-pciback: Document the various parameters and attributes in SysFS
> >       xen/pciback: Don't deadlock when unbinding.
> >       xen/pciback: Include the domain id if removing the device whilst still in use
> >       xen/pciback: Print out the domain owning the device.
> >       xen/pciback: Remove tons of dereferences
> 
> >  Documentation/ABI/testing/sysfs-driver-pciback |   25 +++++++++++++++
> >  drivers/xen/xen-pciback/passthrough.c          |    9 ++++-
> >  drivers/xen/xen-pciback/pci_stub.c             |   41 +++++++++++++------------
> >  drivers/xen/xen-pciback/pciback.h              |    7 ++--
> >  drivers/xen/xen-pciback/vpci.c                 |    9 ++++-
> >  drivers/xen/xen-pciback/xenbus.c               |    4 +-
> >  6 files changed, 67 insertions(+), 28 deletions(-)
> 
> Hi Konrad / David,
> 
> Thanks for the fixes in this series, i just tested this series and noticed (as 
> somewhat expected :-) ) it's still lacking a fix for the bug that pciback 
> doesn't properly free / disown a device from a HVM guest.
> 
> This only happens when using "xl pci-detach domain BDF"
>   AND
> when the guest has more than one pci device attached and you remove only ONE of 
> them.
> 
> The pci-detach doesn't show an error, the device is removed from the guest, but 
> it seems it is not internally freed in pciback.
> 
> Below is the sequence and outcome (with some added printk's) for two situations:
> A) Guest has only one pci-device passed through which is then removed, as you can see 
> it's freed in pciback as well.
> 
> B) Guest has two pci-devices passed through from which one is then removed. 
> After that the second is removed as well.
> 
> >From what i recall Konrad thought it could be due to the guest being a HVM and thus the signaling is different from a
> PV-Guest (no pci-front confirming the removal via xenbus). But since it does get freed when it is the last device attached to the guest
> i don't know if that's completely true.
> It's now semi-fixed when doing the 'xl pci-assignable-remove', that seems to force unregistring the device owner, however something still doesn't seem
> right see the second "xl pci-detach" removing the last device from (A), it takes about a minute instead of not more than a second.
> 
> Also note that when on calling "xl pci-assignable-remove" for the last (or only) passed through device for a guest, you don't get the warning messages about
> the device being 'in-use'
> 
> Completely below an diff of the added printk's.
> 
> --
> 
> Sander
> 
> 
> Ad A)
> 
> root@...0:~# xl pci-list router
> Vdev Device
> 05.0 0000:02:00.0
> 06.0 0000:00:1b.0
> 
> root@...0:~# xl pci-assignable-list
> 
> root@...0:~# xl pci-detach router 00:1b.0
> 
> dmesg shows:
> [  434.839156] pciback 0000:00:1b.0: restoring config space at offset 0x10 (was 0x4, writing 0xf7d30004)
> [  434.841745] pciback 0000:00:1b.0: restoring config space at offset 0xc (was 0x0, writing 0x10)
> [  434.844205] pciback 0000:00:1b.0: restoring config space at offset 0x4 (was 0x100000, writing 0x100006)
> 
> xl dmesg shows:
> (XEN) [2014-07-14 16:02:27] memory_map:remove: dom1 gfn=f3070 mfn=f7d30 nr=4
> (XEN) [2014-07-14 16:02:27] io.c:322: d1: unbind: m_gsi=22 g_gsi=40 dev=00:00.6 intx=0
> (XEN) [2014-07-14 16:02:27] io.c:390: d1 unmap: m_irq=22 dev=00:00.6 intx=0
> (XEN) [2014-07-14 16:02:27] [VT-D]iommu.c:1579: d1:PCIe: unmap 0000:00:1b.0
> (XEN) [2014-07-14 16:02:27] [VT-D]iommu.c:1440: d0:PCIe: map 0000:00:1b.0
> 
> root@...0:~# xl pci-assignable-list
> 0000:00:1b.0
> 
> root@...0:~# xl pci-assignable-remove 00:1b.0
> dmesg shows:
> [  609.246406] xen_pciback: ****** removing device 0000:00:1b.0 while still in-use by domain 1! ******
> [  609.248985] xen_pciback: ****** driver domain may still access this device's i/o resources!
> [  609.251344] xen_pciback: ****** shutdown driver domain before binding device
> [  609.253291] xen_pciback: ****** to other drivers or domains
> [  609.355083] xen: xen_unregister_device_domain_owner
> [  609.356448] xen: xen_unregister_device_domain_owner
> [  609.357789] xen: xen_unregister_device_domain_owner: ENODEV
> [  609.463125] pciback 0000:00:1b.0: restoring config space at offset 0x10 (was 0x4, writing 0xf7d30004)
> [  609.465692] pciback 0000:00:1b.0: restoring config space at offset 0xc (was 0x0, writing 0x10)
> [  609.468137] pciback 0000:00:1b.0: restoring config space at offset 0x4 (was 0x100000, writing 0x100006)
> 
> root@...0:~# xl pci-list router
> Vdev Device
> 05.0 0000:02:00.0
> 
> root@...0:~# xl pci-detach router 02:00.0
> dmesg shows:
> [  930.571300] pciback 0000:02:00.0: restoring config space at offset 0x3c (was 0x100, writing 0x104)
> [  930.574140] pciback 0000:02:00.0: restoring config space at offset 0x10 (was 0x4, writing 0xf7c00004)
> [  930.576859] pciback 0000:02:00.0: restoring config space at offset 0x4 (was 0x100000, writing 0x100006)
> [  930.614554] xen-pciback pci-1-0: xen_pcibk_xenbus_remove freeing pdev @ 0xffff880058fcb480
> [  930.615606] xen-pciback pci-1-0: xen_pcibk_disconnect pdev @ 0xffff880058fcb480
> [  930.719110] xen: xen_unregister_device_domain_owner
> 
> xl dmesg shows:
> (XEN) [2014-07-14 16:10:43] [VT-D]iommu.c:1579: d1:PCIe: unmap 0000:02:00.0
> (XEN) [2014-07-14 16:10:43] [VT-D]iommu.c:1440: d0:PCIe: map 0000:02:00.0
> (XEN) [2014-07-14 16:11:46] memory_map:remove: dom1 gfn=f3074 mfn=f7c00 nr=2
> (XEN) [2014-07-14 16:11:46] io.c:322: d1: unbind: m_gsi=18 g_gsi=36 dev=00:00.5 intx=0
> (XEN) [2014-07-14 16:11:46] io.c:390: d1 unmap: m_irq=18 dev=00:00.5 intx=0
> 
> root@...0:~# xl pci-assignable-list
> 0000:02:00.0
> 
> root@...0:~# xl pci-assignable-remove 02:00.0
> dmesg shows:
> [ 1468.561071] xen: xen_unregister_device_domain_owner
> [ 1468.562431] xen: xen_unregister_device_domain_owner: ENODEV
> [ 1468.667271] pciback 0000:02:00.0: restoring config space at offset 0x3c (was 0x100, writing 0x104)
> [ 1468.670119] pciback 0000:02:00.0: restoring config space at offset 0x10 (was 0x4, writing 0xf7c00004)
> [ 1468.672857] pciback 0000:02:00.0: restoring config space at offset 0x4 (was 0x100000, writing 0x100006)
> 
>

At this point if you do:


#xl pci-assignable-list

I presume you don't see anything
 
> Ad B)
> 
> root@...0:~# xl pci-list router
> Vdev Device
> 05.0 0000:00:1b.0
> 
> root@...0:~# xl pci-assignable-list
> 0000:02:00.0
> 
> root@...0:~# xl pci-detach router 00:1b.0
> dmesg shows:
> [  199.742668] pciback 0000:00:1b.0: restoring config space at offset 0x10 (was 0x4, writing 0xf7d30004)
> [  199.743527] pciback 0000:00:1b.0: restoring config space at offset 0xc (was 0x0, writing 0x10)
> [  199.744321] pciback 0000:00:1b.0: restoring config space at offset 0x4 (was 0x100000, writing 0x100006)
> [  199.757184] xen-pciback pci-1-0: xen_pcibk_xenbus_remove freeing pdev @ 0xffff8800589fce40
> [  199.758139] xen-pciback pci-1-0: xen_pcibk_disconnect pdev @ 0xffff8800589fce40
> [  199.862595] xen: xen_unregister_device_domain_owner
> 
> xl dmesg shows:
> (XEN) [2014-07-14 16:28:29] memory_map:remove: dom1 gfn=f3070 mfn=f7d30 nr=4
> (XEN) [2014-07-14 16:28:29] io.c:322: d1: unbind: m_gsi=22 g_gsi=36 dev=00:00.5 intx=0
> (XEN) [2014-07-14 16:28:29] io.c:390: d1 unmap: m_irq=22 dev=00:00.5 intx=0
> (XEN) [2014-07-14 16:28:29] [VT-D]iommu.c:1579: d1:PCIe: unmap 0000:00:1b.0
> (XEN) [2014-07-14 16:28:29] [VT-D]iommu.c:1440: d0:PCIe: map 0000:00:1b.0
> 
> root@...0:~# xl pci-list router
> root@...0:~# xl pci-assignable-list
> 0000:00:1b.0
> 0000:02:00.0
> 
> root@...0:~# xl pci-assignable-remove 00:1b.0
> dmesg shows:
> [  318.827415] xen: xen_unregister_device_domain_owner
> [  318.828771] xen: xen_unregister_device_domain_owner: ENODEV
> [  318.930869] pciback 0000:00:1b.0: restoring config space at offset 0x10 (was 0x4, writing 0xf7d30004)
> [  318.933435] pciback 0000:00:1b.0: restoring config space at offset 0xc (was 0x0, writing 0x10)
> [  318.935877] pciback 0000:00:1b.0: restoring config space at offset 0x4 (was 0x100000, writing 0x100006)
> 
> root@...0:~# xl pci-list router
> root@...0:~# xl pci-assignable-list
> 0000:02:00.0
> 
> 

And if you do:

# xl pci-detach router 02:00.0

Do you see it being cleared from pciback? And what do you
see in /sys/bus/pci/drivers/pciback ?


Thanks!
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