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Date:	Mon, 14 Jul 2014 14:45:47 -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 08:24:33PM +0200, Sander Eikelenboom wrote:
> 
> Monday, July 14, 2014, 7:45:25 PM, you wrote:
> 
> > On Mon, Jul 14, 2014 at 07:43:04PM +0200, Sander Eikelenboom wrote:
> >> 
> >> Monday, July 14, 2014, 7:37:53 PM, you wrote:
> >> 
> >> >> >> 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
> >> >> 
> >> 
> >> > Err, I meant
> >> > # xl pci-assignable-remove 02:00.0
> >> 
> >> Ah ok .. so that is:
> >> remove a device from pciback that has never been assigned to any guest .. 
> >> 
> >> will also give that a go .. although that probably won't be a problem. 
> 
> > Right. So I think it all works as expected? That is if you have
> > two PCI devices assigned to a guest and want to re-use them you
> > have to do the 'pci-detach' twice and then follow that with
> >  'pci-assignable-remove' twice as well?
> 
> Well except that's not what i want :-) .. that's about the same as shutting down 
> the guest .. and indeed that works :-)
> 
> What i want to do is to remove just *one* device and leave the other one in the guest.
> 
> The one that i remove .. i would like to be able to remove it from being 
> assignable .. (rebind it in dom0) and/or assign it to another guest.

Aha
> 
> And that fails because pciback still thinks the guest owns the device ..
> while libxl thinks it doesn't (outcome of xl pci-assignable-list).

Oh
> 
> When doing the:
> 
> # xl pci-assignable-list
> 0000:02:00.0
> # xl pci-assignable-remove 02:00.0
> dmesg shows:               
> [  443.292951] xen: xen_unregister_device_domain_owner
> [  443.294308] xen: xen_unregister_device_domain_owner: ENODEV
> [  443.398827] pciback 0000:02:00.0: restoring config space at offset 0x3c (was 0x100, writing 0x104)
> [  443.400797] pciback 0000:02:00.0: restoring config space at offset 0x10 (was 0x4, writing 0xf7c00004)
> [  443.401713] pciback 0000:02:00.0: restoring config space at offset 0x4 (was 0x100000, writing 0x100006)
> 
> which i think is what is expected ..

Right.

> 
> 
> Hmm  /sys/bus/pci/drivers/pciback  doesn't shed much light, because in the state 
> just after a xl pci-detach, the device is still registred by pciback (from dom0's 
> view) which is correct, what is wrong is that pciback still seems to think that 
> it is in turn still owned by the guest. That doesn't get reflected in the info 
> available in the /sys dir.

Oh
> 
> Ok over to xen-store ... 

I think I had a patch for that in libxl. It was the order of operations it was
doing - it did the 'unbind' first and then it did the XenBus operations.

> 
> first a diff between the booted guest with two devices passed through and the 
> state after the "xl pci-detach router 00:1b.0"
> 
> root@...anuc:~# diff -U10 xs-before-detach-first.txt xs-after-detach-first.txt
> --- xs-before-detach-first.txt  2014-07-14 19:56:23.233576000 +0200
> +++ xs-after-detach-first.txt   2014-07-14 20:00:00.053576000 +0200
> @@ -185,35 +185,29 @@
>         feature-rx-flip = "0"
>         feature-split-event-channels = "1"
>         multi-queue-max-queues = "4"
>         hotplug-status = "connected"
>      pci = ""
>       1 = ""
>        0 = ""
>         frontend = "/local/domain/1/device/pci/0"
>         frontend-id = "1"
>         online = "1"
> -       state = "3"
> +       state = "7"
>         domain = "router"
>         key-0 = "0000:02:00.0"
>         dev-0 = "0000:02:00.0"
>         vdevfn-0 = "28"
>         opts-0 = "msitranslate=0,power_mgmt=0,permissive=0"
>         state-0 = "3"
> -       key-1 = "0000:00:1b.0"
> -       dev-1 = "0000:00:1b.0"
> -       vdevfn-1 = "30"
> -       opts-1 = "msitranslate=0,power_mgmt=0,permissive=0"
> -       state-1 = "3"
> -       num_devs = "2"
> +       num_devs = "1"
>         vdev-0 = "0000:00:00.00"
> -       vdev-1 = "0000:00:01.00"
>         root-0 = "0000:00"
>         root_num = "1"
>    1 = ""
>     vm = "/vm/a102d97e-8388-414e-97e5-cc394656c47d"
>     name = "router"
>     cpu = ""
>      0 = ""
>       availability = "online"
>      1 = ""
>       availability = "online"
> 
> It seems ok, perhaps apart from the general pci state going from 3 to 7 ?
> Haven't looked up the exact states, but since only one domain is removes i would 
> still expect it to be 3 ?

7 is Reconfiguring which is what it should move to (to update the XenBus).
> 
> 
> Now a diff before and after the "xl pci-assignable-remove 00:1b.0"
> diff xs-after-detach-first.txt xs-after-pci-assignable-remove-first.txt is 
> empty, as expected since this is a pciback only thing now involving any guest.
> 
> 
> And now the last diff, between the state before and after the "xl pci-detach 
> 02:00.0" removing the last pci device from the guest.
> 
> root@...anuc:~# diff -U5 xs-after-pci-assignable-remove-first.txt xs-after-pci-detach-second.txt
> --- xs-after-pci-assignable-remove-first.txt    2014-07-14 20:00:45.161576000 +0200
> +++ xs-after-pci-detach-second.txt      2014-07-14 20:01:20.177576000 +0200
> @@ -184,27 +184,10 @@
>         feature-rx-copy = "1"
>         feature-rx-flip = "0"
>         feature-split-event-channels = "1"
>         multi-queue-max-queues = "4"
>         hotplug-status = "connected"
> -    pci = ""
> -     1 = ""
> -      0 = ""
> -       frontend = "/local/domain/1/device/pci/0"
> -       frontend-id = "1"
> -       online = "1"
> -       state = "7"
> -       domain = "router"
> -       key-0 = "0000:02:00.0"
> -       dev-0 = "0000:02:00.0"
> -       vdevfn-0 = "28"
> -       opts-0 = "msitranslate=0,power_mgmt=0,permissive=0"
> -       state-0 = "3"
> -       num_devs = "1"
> -       vdev-0 = "0000:00:00.00"
> -       root-0 = "0000:00"
> -       root_num = "1"
>    1 = ""
>     vm = "/vm/a102d97e-8388-414e-97e5-cc394656c47d"
>     name = "router"
>     cpu = ""
>      0 = ""
> @@ -249,15 +232,10 @@
>        event-channel-rx = "25"
>        request-rx-copy = "1"
>        feature-rx-notify = "1"
>        feature-sg = "1"
>        feature-gso-tcpv4 = "1"
> -    pci = ""
> -     0 = ""
> -      backend = "/local/domain/0/backend/pci/1/0"
> -      backend-id = "0"
> -      state = "1"
>     control = ""
>      shutdown = ""
>      platform-feature-multiprocessor-suspend = "1"
>      platform-feature-xs_reset_watches = "1"
>     hvmloader = ""
> 
> That seems ok.
> 
> So apart from that perhaps incorrect general pci state change, the info in 
> xenstore seems to be OK.
> 
> So it does seem to be a lack of pciback receiving a confirm from libxl / qemu that the 
> device is indeed removed from the guest for the final deregistring of the 
> ownership.
> 
> Because after a pci-detach the pci device is:
> - removed from xen-store as attached to the guest
> - the iommu has assigned/mapped it back to dom0
> - xl pci-assignable-list shows it as assignable again
> 
> So only pciback is the only one left out of the party :-)
> Couldn't it be somehow tied to the iommu events, since it should be in sync with that i suppose ?


Let me find out what is up with this. Once the device
is de-assigned from a guest (even if forcefully) it should
be possible to assign it to another.

> 
> --
> Sander
> 
> BTW, i don't see the "do_flr" anywhere in /sys/*/pciback/ ?

We been having a lengthy discussion about this and David is out
on vacation so will have to wait until he is back.
> 

View attachment "libxl_pci.patch" of type "text/plain" (1283 bytes)

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