Xen devel - Jun 2013 - xl pci-detach vs xm pci-detach in Xen 4.3 (one works, the other does not)

Something is odd. If I do the pci-detach in Xend 
(xm pci-detach latest 0000:01:00.0) the guest tells me:

[   20.866562] pcifront pci-0: Rescanning PCI Frontend Bus 0000:00
[   20.996602] pcifront pci-0: backend going away!
[   20.996824] pci_bus 0000:00: busn_res: [bus 00-ff] is released
[   20.997089] pcifront pci-0: Disconnecting PCI Frontend Buses
[   21.006171] pcifront pci-0: 22 freeing event channel 17

and I want to attach it back (xm pci-attach latest 0000:01:00.0):

# [   78.823076] pcifront pci-0: Installing PCI frontend
[   78.823332] pcifront pci-0: Creating PCI Frontend Bus 0000:00
[   78.823674] pcifront pci-0: PCI host bridge to bus 0000:00
[   78.823686] pci_bus 0000:00: root bus resource [io  0x0000-0xffff]
[   78.823697] pci_bus 0000:00: root bus resource [mem 0x00000000-0xfffffffff]
[   78.823703] pci_bus 0000:00: root bus resource [bus 00-ff]
[   78.823911] pci 0000:00:00.0: [8086:105e] type 00 class 0x020000
[   78.824234] pci 0000:00:00.0: reg 10: [mem 0xfe4a0000-0xfe4bffff]
[   78.824378] pci 0000:00:00.0: reg 14: [mem 0xfe480000-0xfe49ffff]
[   78.824489] pci 0000:00:00.0: reg 18: [io  0xe020-0xe03f]
[   78.827837] pcifront pci-0: claiming resource 0000:00:00.0/0
[   78.827845] pcifront pci-0: claiming resource 0000:00:00.0/1
[   78.827850] pcifront pci-0: claiming resource 0000:00:00.0/2
[   78.831779] e1000e: Intel(R) PRO/1000 Network Driver - 2.3.2-k
[   78.831790] e1000e: Copyright(c) 1999 - 2013 Intel Corporation.
[   78.831842] e1000e 0000:00:00.0: Disabling ASPM  L1
[   78.831937] e1000e 0000:00:00.0: enabling device (0000 -> 0002)
[   78.834698] xen_map_pirq_gsi: returning irq 34 for gsi 16
[   78.834707] e1000e 0000:00:00.0: Xen PCI mapped GSI16 to IRQ34
[   78.835330] e1000e 0000:00:00.0: Interrupt Throttling Rate (ints/sec) set to
dynamic conservative mode
[   79.002430] e1000e 0000:00:00.0 eth0: (PCI Express:2.5GT/s:Width x4)
00:15:17:8f:18:a2
[   79.002441] e1000e 0000:00:00.0 eth0: Intel(R) PRO/1000 Network Connection
[   79.002521] e1000e 0000:00:00.0 eth0: MAC: 0, PHY: 4, PBA No: D50868-003
[   79.310912] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[   79.313442] device eth0 entered promiscuous mode
[   82.230982] e1000e: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control:
Rx/Tx
[   82.231133] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[   82.231225] switch: port 1(eth0) entered forwarding state
[   82.231242] switch: port 1(eth0) entered forwarding state

Doing this with xl I get:

15:42:23 # 57 :~/
> xl -f pci-detach latest 0000:01:00.0
libxl: error: libxl_pci.c:1231:do_pci_remove: xc_physdev_unmap_pirq irq=82
libxl: error: libxl_pci.c:1235:do_pci_remove: xc_domain_irq_permission irq=82


and in the guest:
# kill -1 1
# [   28.516427] switch: port 1(eth0) entered disabled state
[   28.516590] device eth0 left promiscuous mode
[   28.516599] switch: port 1(eth0) entered disabled state
[   28.547664] pcifront pci-0: Rescanning PCI Frontend Bus 0000:00
[   28.654770] pci_bus 0000:00: busn_res: [bus 00-ff] is released
[   28.654982] pcifront pci-0: 22 freeing event channel 17
[   28.655228] pcifront pci-0: failed to write error node for device/pci/0 (22
freeing event channel 17)


but this with Xen 4.3 that has at its tip:

commit 365c95f7de789e1dca03f119eab7dc61fe0f77c9
Author: Jan Beulich <jbeulich@suse.com>
Date:   Tue Jun 4 09:29:07 2013 +0200

    x86/xsave: properly check guest input to XSETBV

any thoughts? I don''t know if this is a regression or not, but the
libxl errors are pointing me to the recent XSA issue - which I thought
was fixed?

Guest config:
extra="console=hvc0 debug "
kernel="/mnt/lab/latest/vmlinuz"
ramdisk="/mnt/lab/latest/initramfs.cpio.gz"
memory=1024
vcpus=2
name="latest"
on_crash="preserve"
vnc=1
vnclisten="0.0.0.0"
pci=["01:00.0"]
e820_host=1
disk=[''phy:/dev/sdb2,xvda,w'']

create ^
title it xl pci-detach failure
thanks

On Fri, Jun 7, 2013 at 4:45 PM, Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> wrote:
> any thoughts? I don''t know if this is a regression or not, but the
> libxl errors are pointing me to the recent XSA issue - which I thought
> was fixed?
I think the recent issue was with xend not working.  Did we fix send
and break xl?

In any case, this is a pretty important feature; I think we need to
sort it out before release, so I''m giving it a bug id to track.

Is "pci permissive" set in the global xl.conf file?

Have you tried this with say, a stock Debian Wheezy kernel?

 -George

Processing commands for xen@bugs.xenproject.org:
> create ^
Created new bug #12 rooted at
`<20130607154553.GC24882@phenom.dumpdata.com>''
Title: `Re: [Xen-devel] xl pci-detach vs xm pci-detach in Xen 4.3 (one works,
the other does not)''
> title it xl pci-detach failure
Set title for #12 to `xl pci-detach failure''
> thanks
Finished processing.

Modified/created Bugs:
 - 12: http://bugs.xenproject.org/xen/bug/12 (new)

---
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On Mon, Jun 10, 2013 at 12:12:47PM +0100, George Dunlap
wrote:
> create ^
> title it xl pci-detach failure
> thanks
> 
> On Fri, Jun 7, 2013 at 4:45 PM, Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com> wrote:
> > any thoughts? I don''t know if this is a regression or not,
but the
> > libxl errors are pointing me to the recent XSA issue - which I thought
> > was fixed?
> 
> I think the recent issue was with xend not working.  Did we fix send
> and break xl?
Could be. It might also be that that ''xl'' never did it the
same way
as ''xend'' (meaning this might be a XenBus teardown change).

Note also that this is PV guests - and I think most of the testing
had been with the HVM guests with PCI passthrough. So it might be a
seperate issue altogether. Or that nobody tried doing PCI plug/unplug
in the past :-(
> 
> In any case, this is a pretty important feature; I think we need to
> sort it out before release, so I''m giving it a bug id to track.
> 
> Is "pci permissive" set in the global xl.conf file?
No. Let me of course try that.
> 
> Have you tried this with say, a stock Debian Wheezy kernel?
No. A v3.10-rc4 with Xen 4.3 latest.

Is Debian Wheezy a 2.6.32 kernel?
> 
>  -George
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel
>

On 10/06/13 14:20, Konrad Rzeszutek Wilk wrote:
> On Mon, Jun 10, 2013 at 12:12:47PM +0100, George Dunlap wrote:
>> create ^
>> title it xl pci-detach failure
>> thanks
>>
>> On Fri, Jun 7, 2013 at 4:45 PM, Konrad Rzeszutek Wilk
>> <konrad.wilk@oracle.com> wrote:
>>> any thoughts? I don''t know if this is a regression or not,
but the
>>> libxl errors are pointing me to the recent XSA issue - which I
thought
>>> was fixed?
>> I think the recent issue was with xend not working.  Did we fix send
>> and break xl?
> Could be. It might also be that that ''xl'' never did it
the same way
> as ''xend'' (meaning this might be a XenBus teardown
change).
>
> Note also that this is PV guests - and I think most of the testing
> had been with the HVM guests with PCI passthrough. So it might be a
> seperate issue altogether. Or that nobody tried doing PCI plug/unplug
> in the past :-(
I certainly did before my February FOSDEM talk that included driver domains.
>
>> In any case, this is a pretty important feature; I think we need to
>> sort it out before release, so I''m giving it a bug id to
track.
>>
>> Is "pci permissive" set in the global xl.conf file?
> No. Let me of course try that.
That really should have to do with getting it working in the first 
place, not detaching it; but still...
>> Have you tried this with say, a stock Debian Wheezy kernel?
> No. A v3.10-rc4 with Xen 4.3 latest.
>
> Is Debian Wheezy a 2.6.32 kernel?
No, 3.2.

  -George

Processing commands for xen@bugs.xenproject.org:
> On Mon, Jun 10, 2013 at 12:12:47PM +0100, George Dunlap wrote:
Command failed: Unknown command `On''. at
/srv/xen-devel-bugs/lib/emesinae/control.pl line 408, <M> line 41.
Stop processing here.

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Processing commands for xen@bugs.xenproject.org:
> On 10/06/13 14:20, Konrad Rzeszutek Wilk wrote:
Command failed: Unknown command `On''. at
/srv/xen-devel-bugs/lib/emesinae/control.pl line 408, <M> line 34.
Stop processing here.

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On Mon, Jun 10, 2013 at 02:28:11PM +0100, George Dunlap
wrote:
> On 10/06/13 14:20, Konrad Rzeszutek Wilk wrote:
> >On Mon, Jun 10, 2013 at 12:12:47PM +0100, George Dunlap wrote:
> >>create ^
> >>title it xl pci-detach failure
> >>thanks
> >>
> >>On Fri, Jun 7, 2013 at 4:45 PM, Konrad Rzeszutek Wilk
> >><konrad.wilk@oracle.com> wrote:
> >>>any thoughts? I don''t know if this is a regression or
not, but the
> >>>libxl errors are pointing me to the recent XSA issue - which I
thought
> >>>was fixed?
> >>I think the recent issue was with xend not working.  Did we fix
send
> >>and break xl?
> >Could be. It might also be that that ''xl'' never did
it the same way
> >as ''xend'' (meaning this might be a XenBus teardown
change).
> >
> >Note also that this is PV guests - and I think most of the testing
> >had been with the HVM guests with PCI passthrough. So it might be a
> >seperate issue altogether. Or that nobody tried doing PCI plug/unplug
> >in the past :-(
> 
> I certainly did before my February FOSDEM talk that included driver
domains.
> 
> >
> >>In any case, this is a pretty important feature; I think we need to
> >>sort it out before release, so I''m giving it a bug id to
track.
> >>
> >>Is "pci permissive" set in the global xl.conf file?
> >No. Let me of course try that.
> 
> That really should have to do with getting it working in the first
> place, not detaching it; but still...
> 
> >>Have you tried this with say, a stock Debian Wheezy kernel?
> >No. A v3.10-rc4 with Xen 4.3 latest.
> >
> >Is Debian Wheezy a 2.6.32 kernel?
> 
> No, 3.2.
I figured it out. It is the XenBus states.


The ''xm'' for pci-detach would do:
 4(Connected)->7(Reconfiguring)-> 8(Reconfigured)->
4(Connected)->5(Closing).

While ''xl'' does:
 4(Connected)->7(Reconfiguring)-> 8(Reconfigured)-> 4(Connected)

That means the xen-pcifront never gets told that the connection is going to
be removed and can do its cleanup.

Without the cleanup it fails at the 3->4(Connected) change state:

[  151.403112] pcifront pci-0: publishing successful!
[  151.404313] pcifront pci-0: backend new state: 2 (old state:3)!
[  151.406160] pcifront pci-0: backend new state: 3 (old state:3)!
[  151.407287] pcifront pci-0: backend new state: 4 (old state:3)!
[  151.407463] pcifront pci-0: PCI frontend already installed!
===> [  151.407474] pcifront pci-0: 17 Error setting up PCI Frontend
<====[  151.407680] pcifront pci-0: failed to write error node for
device/pci/0 (17 Error setting up PCI Frontend) ret: -13
[  151.410502] pcifront pci-0: backend new state: 5 (old state:5)!
[  151.410509] pcifront pci-0: backend going away!

B/c the ''PCI frontend already installed'' check has been hit
(new in 3.7)
and would never progress further (see git commit
3d925320e9e2de162bd138bf97816bda8c3f71be - xen/pcifront: Use Xen-SWIOTLB when
initting if required.)


This looks like an OK protocol change so I am inclined to say the Xen pcifront
needs a bit more checking. Sending patches for that shortly.

Processing commands for xen@bugs.xenproject.org:
> On Mon, Jun 10, 2013 at 02:28:11PM +0100, George Dunlap wrote:
Command failed: Unknown command `On''. at
/srv/xen-devel-bugs/lib/emesinae/control.pl line 408, <M> line 43.
Stop processing here.

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Please see attached patch. It fixes it for me.

There are two tool-stack that can instruct the Xen PCI frontend
and backend to change states: ''xm'' (Python code with a
daemon),
and ''xl'' (C library - does not keep state changes).

With the ''xm'', the path to disconnect a PCI device (xm
pci-detach
<guest> <BDF>)is:

4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)->5(Closing*).

The * is for states that the tool-stack sets. For ''xl'', it is
similar:

4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 4(Connected)

Both of them also tear down the XenBus structure, so the backend
state ends up going in the 3(Initialised) and calls pcifront_xenbus_remove.

When a PCI device is plugged in (xm pci-attach <guest> <BDF>)
both of them follow the same pattern:
2(InitWait*), 3(Initialized*), 4(Connected*)->4(Connected).

[xen-pcifront ignores the 2,3 state changes and only acts when
4 (Connected) has been reached]

The problem is that git commit 3d925320e9e2de162bd138bf97816bda8c3f71be
("xen/pcifront: Use Xen-SWIOTLB when initting if required") introduced
a mechanism to initialize the SWIOTLB when the Xen PCI front moves to
Connected state. It also had some aggressive seatbelt code check that
would warn the user if one tried to change to Connected state without
hitting first the Closing state:

 pcifront pci-0: PCI frontend already installed!

However, that code can be relaxed and we can continue on working
even if the frontend is instructed to be the ''Connected'' state
with
no devices and then gets tickled to be in ''Connected'' state
again.

In other words, this 4(Connected)->5(Closing)->4(Connected) state
was expected, while 4(Connected)->.... anything but
5(Closing)->4(Connected)
was not. This patch removes that aggressive check and allows
Xen pcifront to work with the ''xl'' toolstack.

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 drivers/pci/xen-pcifront.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index ac99515..cc46e253 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -675,10 +675,9 @@ static int pcifront_connect_and_init_dma(struct
pcifront_device *pdev)
 	if (!pcifront_dev) {
 		dev_info(&pdev->xdev->dev, "Installing PCI frontend\n");
 		pcifront_dev = pdev;
-	} else {
-		dev_err(&pdev->xdev->dev, "PCI frontend already
installed!\n");
+	} else
 		err = -EEXIST;
-	}
+
 	spin_unlock(&pcifront_dev_lock);
 
 	if (!err && !swiotlb_nr_tbl()) {
@@ -846,7 +845,7 @@ static int pcifront_try_connect(struct pcifront_device
*pdev)
 		goto out;
 
 	err = pcifront_connect_and_init_dma(pdev);
-	if (err) {
+	if (err && err != -EEXIST) {
 		xenbus_dev_fatal(pdev->xdev, err,
 				 "Error setting up PCI Frontend");
 		goto out;
-- 
1.8.1.4

>>> On 10.06.13 at 23:06, Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> wrote:
> There are two tool-stack that can instruct the Xen PCI frontend
> and backend to change states: ''xm'' (Python code with a
daemon),
> and ''xl'' (C library - does not keep state changes).
> 
> With the ''xm'', the path to disconnect a PCI device (xm
pci-detach
> <guest> <BDF>)is:
> 
> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)->5(Closing*).
> 
> The * is for states that the tool-stack sets. For ''xl'',
it is similar:
> 
> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 4(Connected)
> 
> Both of them also tear down the XenBus structure, so the backend
> state ends up going in the 3(Initialised) and calls pcifront_xenbus_remove.
> 
> When a PCI device is plugged in (xm pci-attach <guest> <BDF>)
> both of them follow the same pattern:
> 2(InitWait*), 3(Initialized*), 4(Connected*)->4(Connected).
> 
> [xen-pcifront ignores the 2,3 state changes and only acts when
> 4 (Connected) has been reached]
> 
> The problem is that git commit 3d925320e9e2de162bd138bf97816bda8c3f71be
> ("xen/pcifront: Use Xen-SWIOTLB when initting if required")
introduced
> a mechanism to initialize the SWIOTLB when the Xen PCI front moves to
> Connected state. It also had some aggressive seatbelt code check that
> would warn the user if one tried to change to Connected state without
> hitting first the Closing state:
> 
>  pcifront pci-0: PCI frontend already installed!
> 
> However, that code can be relaxed and we can continue on working
> even if the frontend is instructed to be the ''Connected''
state with
> no devices and then gets tickled to be in ''Connected''
state again.
> 
> In other words, this 4(Connected)->5(Closing)->4(Connected) state
> was expected, while 4(Connected)->.... anything but
5(Closing)->4(Connected)
> was not. This patch removes that aggressive check and allows
> Xen pcifront to work with the ''xl'' toolstack.
I actually think this shouldn''t be worked around here, but fixed in
xl. Any device removed from a guest should be driven towards
the "Closed" state.

Jan
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: linux-pci@vger.kernel.org 
> Cc: stable@vger.kernel.org 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  drivers/pci/xen-pcifront.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> index ac99515..cc46e253 100644
> --- a/drivers/pci/xen-pcifront.c
> +++ b/drivers/pci/xen-pcifront.c
> @@ -675,10 +675,9 @@ static int pcifront_connect_and_init_dma(struct 
> pcifront_device *pdev)
>  	if (!pcifront_dev) {
>  		dev_info(&pdev->xdev->dev, "Installing PCI
frontend\n");
>  		pcifront_dev = pdev;
> -	} else {
> -		dev_err(&pdev->xdev->dev, "PCI frontend already
installed!\n");
> +	} else
>  		err = -EEXIST;
> -	}
> +
>  	spin_unlock(&pcifront_dev_lock);
>  
>  	if (!err && !swiotlb_nr_tbl()) {
> @@ -846,7 +845,7 @@ static int pcifront_try_connect(struct pcifront_device 
> *pdev)
>  		goto out;
>  
>  	err = pcifront_connect_and_init_dma(pdev);
> -	if (err) {
> +	if (err && err != -EEXIST) {
>  		xenbus_dev_fatal(pdev->xdev, err,
>  				 "Error setting up PCI Frontend");
>  		goto out;
> -- 
> 1.8.1.4
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org 
> http://lists.xen.org/xen-devel

On 06/11/2013 08:29 AM, Jan Beulich wrote:
>>>> On 10.06.13 at 23:06, Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> wrote:
>> There are two tool-stack that can instruct the Xen PCI frontend
>> and backend to change states: ''xm'' (Python code with
a daemon),
>> and ''xl'' (C library - does not keep state changes).
>>
>> With the ''xm'', the path to disconnect a PCI device
(xm pci-detach
>> <guest> <BDF>)is:
>>
>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)->5(Closing*).
>>
>> The * is for states that the tool-stack sets. For
''xl'', it is similar:
>>
>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)
>>
>> Both of them also tear down the XenBus structure, so the backend
>> state ends up going in the 3(Initialised) and calls
pcifront_xenbus_remove.
>>
>> When a PCI device is plugged in (xm pci-attach <guest>
<BDF>)
>> both of them follow the same pattern:
>> 2(InitWait*), 3(Initialized*), 4(Connected*)->4(Connected).
>>
>> [xen-pcifront ignores the 2,3 state changes and only acts when
>> 4 (Connected) has been reached]
>>
>> The problem is that git commit 3d925320e9e2de162bd138bf97816bda8c3f71be
>> ("xen/pcifront: Use Xen-SWIOTLB when initting if required")
introduced
>> a mechanism to initialize the SWIOTLB when the Xen PCI front moves to
>> Connected state. It also had some aggressive seatbelt code check that
>> would warn the user if one tried to change to Connected state without
>> hitting first the Closing state:
>>
>>   pcifront pci-0: PCI frontend already installed!
>>
>> However, that code can be relaxed and we can continue on working
>> even if the frontend is instructed to be the
''Connected'' state with
>> no devices and then gets tickled to be in ''Connected''
state again.
>>
>> In other words, this 4(Connected)->5(Closing)->4(Connected) state
>> was expected, while 4(Connected)->.... anything but
5(Closing)->4(Connected)
>> was not. This patch removes that aggressive check and allows
>> Xen pcifront to work with the ''xl'' toolstack.
>
> I actually think this shouldn''t be worked around here, but fixed
in
> xl. Any device removed from a guest should be driven towards
> the "Closed" state.
Yeah, that seems pretty obvious to me.  The weird thing is that this 
wasn''t noticed before -- does this work in 4.2?  Have you been doing 
this test all along, or has it only broken recently?

I''ve reproduced it on one of my test boxes; let me see if I can sort it
out.

  -George

On 6/11/2013 5:00 AM, George Dunlap wrote:
> On 06/11/2013 08:29 AM, Jan Beulich wrote:
>>>>> On 10.06.13 at 23:06, Konrad Rzeszutek Wilk 
>>>>> <konrad.wilk@oracle.com> wrote:
>>> There are two tool-stack that can instruct the Xen PCI frontend
>>> and backend to change states: ''xm'' (Python code
with a daemon),
>>> and ''xl'' (C library - does not keep state
changes).
>>>
>>> With the ''xm'', the path to disconnect a PCI
device (xm pci-detach
>>> <guest> <BDF>)is:
>>>
>>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 
>>> 4(Connected)->5(Closing*).
>>>
>>> The * is for states that the tool-stack sets. For
''xl'', it is similar:
>>>
>>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)
>>>
>>> Both of them also tear down the XenBus structure, so the backend
>>> state ends up going in the 3(Initialised) and calls 
>>> pcifront_xenbus_remove.
>>>
>>> When a PCI device is plugged in (xm pci-attach <guest>
<BDF>)
>>> both of them follow the same pattern:
>>> 2(InitWait*), 3(Initialized*), 4(Connected*)->4(Connected).
>>>
>>> [xen-pcifront ignores the 2,3 state changes and only acts when
>>> 4 (Connected) has been reached]
>>>
>>> The problem is that git commit
3d925320e9e2de162bd138bf97816bda8c3f71be
>>> ("xen/pcifront: Use Xen-SWIOTLB when initting if
required") introduced
>>> a mechanism to initialize the SWIOTLB when the Xen PCI front moves
to
>>> Connected state. It also had some aggressive seatbelt code check
that
>>> would warn the user if one tried to change to Connected state
without
>>> hitting first the Closing state:
>>>
>>>   pcifront pci-0: PCI frontend already installed!
>>>
>>> However, that code can be relaxed and we can continue on working
>>> even if the frontend is instructed to be the
''Connected'' state with
>>> no devices and then gets tickled to be in
''Connected'' state again.
>>>
>>> In other words, this 4(Connected)->5(Closing)->4(Connected)
state
>>> was expected, while 4(Connected)->.... anything but 
>>> 5(Closing)->4(Connected)
>>> was not. This patch removes that aggressive check and allows
>>> Xen pcifront to work with the ''xl'' toolstack.
>>
>> I actually think this shouldn''t be worked around here, but
fixed in
>> xl. Any device removed from a guest should be driven towards
>> the "Closed" state.
There is also the per-device state. Those are moved to the 5 (Closing), 
while the
whole connection is still in the 4(Connected) state. In essence all of 
the per-device states
are closed, it is just that the global state is still Connected.

>
> Yeah, that seems pretty obvious to me.  The weird thing is that this 
> wasn''t noticed before -- does this work in 4.2?  Have you been
doing
> this test all along, or has it only broken recently?
I just reproduced this in Xen 4.2. I believe that the reason I did not 
see this before was b/c I was using ''xm''
primarily.
>
> I''ve reproduced it on one of my test boxes; let me see if I can
sort
> it out.
OK.
>
>  -George
>

On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote:
> There are two tool-stack that can instruct the Xen PCI frontend
> and backend to change states: ''xm'' (Python code with a
daemon),
> and ''xl'' (C library - does not keep state changes).
>
> With the ''xm'', the path to disconnect a PCI device (xm
pci-detach
> <guest> <BDF>)is:
>
> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)->5(Closing*).
>
> The * is for states that the tool-stack sets. For ''xl'',
it is similar:
>
> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 4(Connected)
>
> Both of them also tear down the XenBus structure, so the backend
> state ends up going in the 3(Initialised) and calls pcifront_xenbus_remove.
So I looked a little bit into this; there are actually two different 
states that happen as part of this handshake.  In order to disonnect a 
*device*, xl signals using the *bus* state, like this:
* Wait for the *bus* to be in state 4(Connected)
* Set the *device* state to 5(Closing)
* Set the *bus* state to 7(Reconfiguring)
* Wait for the *bus* state to return to 4(Connected)

So are all of these states you see the *bus* state?  And why would you 
disconnect the whole pci bus if you''re only removing one device?

  -George

On 6/11/2013 11:36 AM, George Dunlap wrote:
> On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote:
>> There are two tool-stack that can instruct the Xen PCI frontend
>> and backend to change states: ''xm'' (Python code with
a daemon),
>> and ''xl'' (C library - does not keep state changes).
>>
>> With the ''xm'', the path to disconnect a PCI device
(xm pci-detach
>> <guest> <BDF>)is:
>>
>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 
>> 4(Connected)->5(Closing*).
>>
>> The * is for states that the tool-stack sets. For
''xl'', it is similar:
>>
>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)
>>
>> Both of them also tear down the XenBus structure, so the backend
>> state ends up going in the 3(Initialised) and calls 
>> pcifront_xenbus_remove.
>
> So I looked a little bit into this; there are actually two different 
> states that happen as part of this handshake.  In order to disonnect a 
> *device*, xl signals using the *bus* state, like this:
> * Wait for the *bus* to be in state 4(Connected)
> * Set the *device* state to 5(Closing)
> * Set the *bus* state to 7(Reconfiguring)
> * Wait for the *bus* state to return to 4(Connected)
>
> So are all of these states you see the *bus* state?  And why would you 
> disconnect the whole pci bus if you''re only removing one device?
Correct. The stats I enumerated are *bus* states. Not per-device states.
I presume (and I hadn''t checked xm) that Xend has some logic to only 
disconnect the bus if all of the PCI devices have been disconnected. In 
''xl'' it does not do that.

The testing I did was just with one PCI device.
>
>  -George

On 06/11/2013 05:08 PM, konrad wilk wrote:
>
> On 6/11/2013 11:36 AM, George Dunlap wrote:
>> On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote:
>>> There are two tool-stack that can instruct the Xen PCI frontend
>>> and backend to change states: ''xm'' (Python code
with a daemon),
>>> and ''xl'' (C library - does not keep state
changes).
>>>
>>> With the ''xm'', the path to disconnect a PCI
device (xm pci-detach
>>> <guest> <BDF>)is:
>>>
>>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
>>> 4(Connected)->5(Closing*).
>>>
>>> The * is for states that the tool-stack sets. For
''xl'', it is similar:
>>>
>>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)
>>>
>>> Both of them also tear down the XenBus structure, so the backend
>>> state ends up going in the 3(Initialised) and calls
>>> pcifront_xenbus_remove.
>>
>> So I looked a little bit into this; there are actually two different
>> states that happen as part of this handshake.  In order to disonnect a
>> *device*, xl signals using the *bus* state, like this:
>> * Wait for the *bus* to be in state 4(Connected)
>> * Set the *device* state to 5(Closing)
>> * Set the *bus* state to 7(Reconfiguring)
>> * Wait for the *bus* state to return to 4(Connected)
>>
>> So are all of these states you see the *bus* state?  And why would you
>> disconnect the whole pci bus if you''re only removing one
device?
>
> Correct. The stats I enumerated are *bus* states. Not per-device states.
> I presume (and I hadn''t checked xm) that Xend has some logic to
only
> disconnect the bus if all of the PCI devices have been disconnected. In
> ''xl'' it does not do that.
>
> The testing I did was just with one PCI device.
Ah, OK -- I see now.  The problem is that the code in the Linux side 
didn''t know about the whole "4->7->8->4" thing to
unplug a device.  In
all likelihood, if you had used xm with two devices (so that the bus 
didn''t get disconnected), then you would have run across the same
error.

So at least part of the problem *is* a bug in Linux.

That doesn''t explain why I have problems doing this on
Debian''s version
of 3.2 -- unless the "fix" you mentoned above was backported to the 
stable kernel, perhaps?

  -George

On 6/11/2013 12:17 PM, George Dunlap wrote:
> On 06/11/2013 05:08 PM, konrad wilk wrote:
>>
>> On 6/11/2013 11:36 AM, George Dunlap wrote:
>>> On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote:
>>>> There are two tool-stack that can instruct the Xen PCI frontend
>>>> and backend to change states: ''xm'' (Python
code with a daemon),
>>>> and ''xl'' (C library - does not keep state
changes).
>>>>
>>>> With the ''xm'', the path to disconnect a PCI
device (xm pci-detach
>>>> <guest> <BDF>)is:
>>>>
>>>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
>>>> 4(Connected)->5(Closing*).
>>>>
>>>> The * is for states that the tool-stack sets. For
''xl'', it is similar:
>>>>
>>>> 4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)
>>>>
>>>> Both of them also tear down the XenBus structure, so the
backend
>>>> state ends up going in the 3(Initialised) and calls
>>>> pcifront_xenbus_remove.
>>>
>>> So I looked a little bit into this; there are actually two
different
>>> states that happen as part of this handshake.  In order to
disonnect a
>>> *device*, xl signals using the *bus* state, like this:
>>> * Wait for the *bus* to be in state 4(Connected)
>>> * Set the *device* state to 5(Closing)
>>> * Set the *bus* state to 7(Reconfiguring)
>>> * Wait for the *bus* state to return to 4(Connected)
>>>
>>> So are all of these states you see the *bus* state?  And why would
you
>>> disconnect the whole pci bus if you''re only removing one
device?
>>
>> Correct. The stats I enumerated are *bus* states. Not per-device
states.
>> I presume (and I hadn''t checked xm) that Xend has some logic
to only
>> disconnect the bus if all of the PCI devices have been disconnected. In
>> ''xl'' it does not do that.
>>
>> The testing I did was just with one PCI device.
>
> Ah, OK -- I see now.  The problem is that the code in the Linux side 
> didn''t know about the whole "4->7->8->4" thing
to unplug a device.  In
> all likelihood, if you had used xm with two devices (so that the bus 
> didn''t get disconnected), then you would have run across the same
error.
>
> So at least part of the problem *is* a bug in Linux.
Right.
>
> That doesn''t explain why I have problems doing this on
Debian''s
> version of 3.2 -- unless the "fix" you mentoned above was
backported
> to the stable kernel, perhaps?
No. It was a feature.
>
>  -George

On Tue, Jun 11, 2013 at 05:17:45PM +0100, George Dunlap
wrote:
> On 06/11/2013 05:08 PM, konrad wilk wrote:
> >
> >On 6/11/2013 11:36 AM, George Dunlap wrote:
> >>On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote:
> >>>There are two tool-stack that can instruct the Xen PCI frontend
> >>>and backend to change states: ''xm'' (Python
code with a daemon),
> >>>and ''xl'' (C library - does not keep state
changes).
> >>>
> >>>With the ''xm'', the path to disconnect a PCI
device (xm pci-detach
> >>><guest> <BDF>)is:
> >>>
> >>>4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
> >>>4(Connected)->5(Closing*).
> >>>
> >>>The * is for states that the tool-stack sets. For
''xl'', it is similar:
> >>>
> >>>4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)->
4(Connected)
> >>>
> >>>Both of them also tear down the XenBus structure, so the
backend
> >>>state ends up going in the 3(Initialised) and calls
> >>>pcifront_xenbus_remove.
> >>
> >>So I looked a little bit into this; there are actually two
different
> >>states that happen as part of this handshake.  In order to
disonnect a
> >>*device*, xl signals using the *bus* state, like this:
> >>* Wait for the *bus* to be in state 4(Connected)
> >>* Set the *device* state to 5(Closing)
> >>* Set the *bus* state to 7(Reconfiguring)
> >>* Wait for the *bus* state to return to 4(Connected)
> >>
> >>So are all of these states you see the *bus* state?  And why would
you
> >>disconnect the whole pci bus if you''re only removing one
device?
> >
> >Correct. The stats I enumerated are *bus* states. Not per-device
states.
> >I presume (and I hadn''t checked xm) that Xend has some logic
to only
> >disconnect the bus if all of the PCI devices have been disconnected. In
> >''xl'' it does not do that.
> >
> >The testing I did was just with one PCI device.
> 
> Ah, OK -- I see now.  The problem is that the code in the Linux side
> didn''t know about the whole "4->7->8->4" thing
to unplug a device.
> In all likelihood, if you had used xm with two devices (so that the
> bus didn''t get disconnected), then you would have run across the
> same error.
> 
> So at least part of the problem *is* a bug in Linux.
Good! Bjorn, would you be OK Ack-ing the patch I sent (attached here
for reference) or putting it in your queue for Linus?

My plan would be to send it to Linus in the 3.11 merge window.

On 12/06/13 14:45, Konrad Rzeszutek Wilk wrote:
> On Tue, Jun 11, 2013 at 05:17:45PM +0100, George Dunlap wrote:
>> On 06/11/2013 05:08 PM, konrad wilk wrote:
>>> On 6/11/2013 11:36 AM, George Dunlap wrote:
>>>> On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote:
>>>>> There are two tool-stack that can instruct the Xen PCI
frontend
>>>>> and backend to change states: ''xm''
(Python code with a daemon),
>>>>> and ''xl'' (C library - does not keep state
changes).
>>>>>
>>>>> With the ''xm'', the path to disconnect a
PCI device (xm pci-detach
>>>>> <guest> <BDF>)is:
>>>>>
>>>>> 4(Connected)->7(Reconfiguring*)->
8(Reconfigured)->
>>>>> 4(Connected)->5(Closing*).
>>>>>
>>>>> The * is for states that the tool-stack sets. For
''xl'', it is similar:
>>>>>
>>>>> 4(Connected)->7(Reconfiguring*)->
8(Reconfigured)-> 4(Connected)
>>>>>
>>>>> Both of them also tear down the XenBus structure, so the
backend
>>>>> state ends up going in the 3(Initialised) and calls
>>>>> pcifront_xenbus_remove.
>>>> So I looked a little bit into this; there are actually two
different
>>>> states that happen as part of this handshake.  In order to
disonnect a
>>>> *device*, xl signals using the *bus* state, like this:
>>>> * Wait for the *bus* to be in state 4(Connected)
>>>> * Set the *device* state to 5(Closing)
>>>> * Set the *bus* state to 7(Reconfiguring)
>>>> * Wait for the *bus* state to return to 4(Connected)
>>>>
>>>> So are all of these states you see the *bus* state?  And why
would you
>>>> disconnect the whole pci bus if you''re only removing
one device?
>>> Correct. The stats I enumerated are *bus* states. Not per-device
states.
>>> I presume (and I hadn''t checked xm) that Xend has some
logic to only
>>> disconnect the bus if all of the PCI devices have been
disconnected. In
>>> ''xl'' it does not do that.
>>>
>>> The testing I did was just with one PCI device.
>> Ah, OK -- I see now.  The problem is that the code in the Linux side
>> didn''t know about the whole "4->7->8->4"
thing to unplug a device.
>> In all likelihood, if you had used xm with two devices (so that the
>> bus didn''t get disconnected), then you would have run across
the
>> same error.
>>
>> So at least part of the problem *is* a bug in Linux.
> Good! Bjorn, would you be OK Ack-ing the patch I sent (attached here
> for reference) or putting it in your queue for Linus?
>
> My plan would be to send it to Linus in the 3.11 merge window.
One nit -- "to work with the ''xl'' toolstack" --
didn''t we theorize this
would also be broken with xm if you had two devices passed through?

  -George

On Wed, Jun 12, 2013 at 02:47:11PM +0100, George Dunlap
wrote:
> On 12/06/13 14:45, Konrad Rzeszutek Wilk wrote:
> >On Tue, Jun 11, 2013 at 05:17:45PM +0100, George Dunlap wrote:
> >>On 06/11/2013 05:08 PM, konrad wilk wrote:
> >>>On 6/11/2013 11:36 AM, George Dunlap wrote:
> >>>>On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote:
> >>>>>There are two tool-stack that can instruct the Xen PCI
frontend
> >>>>>and backend to change states: ''xm''
(Python code with a daemon),
> >>>>>and ''xl'' (C library - does not keep
state changes).
> >>>>>
> >>>>>With the ''xm'', the path to disconnect
a PCI device (xm pci-detach
> >>>>><guest> <BDF>)is:
> >>>>>
> >>>>>4(Connected)->7(Reconfiguring*)->
8(Reconfigured)->
> >>>>>4(Connected)->5(Closing*).
> >>>>>
> >>>>>The * is for states that the tool-stack sets. For
''xl'', it is similar:
> >>>>>
> >>>>>4(Connected)->7(Reconfiguring*)->
8(Reconfigured)-> 4(Connected)
> >>>>>
> >>>>>Both of them also tear down the XenBus structure, so
the backend
> >>>>>state ends up going in the 3(Initialised) and calls
> >>>>>pcifront_xenbus_remove.
> >>>>So I looked a little bit into this; there are actually two
different
> >>>>states that happen as part of this handshake.  In order to
disonnect a
> >>>>*device*, xl signals using the *bus* state, like this:
> >>>>* Wait for the *bus* to be in state 4(Connected)
> >>>>* Set the *device* state to 5(Closing)
> >>>>* Set the *bus* state to 7(Reconfiguring)
> >>>>* Wait for the *bus* state to return to 4(Connected)
> >>>>
> >>>>So are all of these states you see the *bus* state?  And
why would you
> >>>>disconnect the whole pci bus if you''re only
removing one device?
> >>>Correct. The stats I enumerated are *bus* states. Not
per-device states.
> >>>I presume (and I hadn''t checked xm) that Xend has some
logic to only
> >>>disconnect the bus if all of the PCI devices have been
disconnected. In
> >>>''xl'' it does not do that.
> >>>
> >>>The testing I did was just with one PCI device.
> >>Ah, OK -- I see now.  The problem is that the code in the Linux
side
> >>didn''t know about the whole
"4->7->8->4" thing to unplug a device.
> >>In all likelihood, if you had used xm with two devices (so that the
> >>bus didn''t get disconnected), then you would have run
across the
> >>same error.
> >>
> >>So at least part of the problem *is* a bug in Linux.
> >Good! Bjorn, would you be OK Ack-ing the patch I sent (attached here
> >for reference) or putting it in your queue for Linus?
> >
> >My plan would be to send it to Linus in the 3.11 merge window.
> 
> One nit -- "to work with the ''xl'' toolstack" --
didn''t we theorize
> this would also be broken with xm if you had two devices passed
> through?
Yes. I will fix up the title to reflect that shortly (say Friday?)

Thanks for your sharp eyes.

On Wed, Jun 12, 2013 at 7:45 AM, Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> wrote:
> On Tue, Jun 11, 2013 at 05:17:45PM +0100, George Dunlap wrote:
>> On 06/11/2013 05:08 PM, konrad wilk wrote:
>> >
>> >On 6/11/2013 11:36 AM, George Dunlap wrote:
>> >>On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote:
>> >>>There are two tool-stack that can instruct the Xen PCI
frontend
>> >>>and backend to change states: ''xm''
(Python code with a daemon),
>> >>>and ''xl'' (C library - does not keep state
changes).
>> >>>
>> >>>With the ''xm'', the path to disconnect a
PCI device (xm pci-detach
>> >>><guest> <BDF>)is:
>> >>>
>> >>>4(Connected)->7(Reconfiguring*)->
8(Reconfigured)->
>> >>>4(Connected)->5(Closing*).
>> >>>
>> >>>The * is for states that the tool-stack sets. For
''xl'', it is similar:
>> >>>
>> >>>4(Connected)->7(Reconfiguring*)->
8(Reconfigured)-> 4(Connected)
>> >>>
>> >>>Both of them also tear down the XenBus structure, so the
backend
>> >>>state ends up going in the 3(Initialised) and calls
>> >>>pcifront_xenbus_remove.
>> >>
>> >>So I looked a little bit into this; there are actually two
different
>> >>states that happen as part of this handshake.  In order to
disonnect a
>> >>*device*, xl signals using the *bus* state, like this:
>> >>* Wait for the *bus* to be in state 4(Connected)
>> >>* Set the *device* state to 5(Closing)
>> >>* Set the *bus* state to 7(Reconfiguring)
>> >>* Wait for the *bus* state to return to 4(Connected)
>> >>
>> >>So are all of these states you see the *bus* state?  And why
would you
>> >>disconnect the whole pci bus if you''re only removing
one device?
>> >
>> >Correct. The stats I enumerated are *bus* states. Not per-device
states.
>> >I presume (and I hadn''t checked xm) that Xend has some
logic to only
>> >disconnect the bus if all of the PCI devices have been
disconnected. In
>> >''xl'' it does not do that.
>> >
>> >The testing I did was just with one PCI device.
>>
>> Ah, OK -- I see now.  The problem is that the code in the Linux side
>> didn''t know about the whole "4->7->8->4"
thing to unplug a device.
>> In all likelihood, if you had used xm with two devices (so that the
>> bus didn''t get disconnected), then you would have run across
the
>> same error.
>>
>> So at least part of the problem *is* a bug in Linux.
>
> Good! Bjorn, would you be OK Ack-ing the patch I sent (attached here
> for reference) or putting it in your queue for Linus?
>
> My plan would be to send it to Linus in the 3.11 merge window.
Sure; this is your baby :)  Why don''t you handle it via your tree,
since it''s more related to xen than any PCI core stuff.

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> >> So at least part of the problem *is* a bug in Linux.
> >
> > Good! Bjorn, would you be OK Ack-ing the patch I sent (attached here
> > for reference) or putting it in your queue for Linus?
> >
> > My plan would be to send it to Linus in the 3.11 merge window.
> 
> Sure; this is your baby :)  Why don''t you handle it via your tree,
> since it''s more related to xen than any PCI core stuff.
OK. Thanks!

Processing commands for xen@bugs.xenproject.org:
> help
Command failed: Unknown command `help''. at
/srv/xen-devel-bugs/lib/emesinae/control.pl line 437, <M> line 43.
Stop processing here.

---
Xen Hypervisor Bug Tracker
See http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen for information on
reporting bugs
Contact xen-bugs-owner@bugs.xenproject.org with any infrastructure issues

On Mon, Nov 04, 2013 at 08:30:01PM +0000, xen@bugs.xenproject.org
wrote:
> Processing commands for xen@bugs.xenproject.org:
> 
> > help
> Command failed: Unknown command `help''. at
/srv/xen-devel-bugs/lib/emesinae/control.pl line 437, <M> line 43.
> Stop processing here.
> 
http://bugs.xenproject.org/xen/static/control.txt

However you might not have permission to do things. :-)

Wei.
> ---
> Xen Hypervisor Bug Tracker
> See http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen for information on
reporting bugs
> Contact xen-bugs-owner@bugs.xenproject.org with any infrastructure issues
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

> Sure; this is your baby :)  Why don''t you handle it via your tree,
> since it''s more related to xen than any PCI core stuff.
> 
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Definitly fixed in v3.12. Just tested it and it works.

George, Ian, how do I "close" a bug in
http://bugs.xenproject.org/xen/bug/12 ?

Processing commands for xen@bugs.xenproject.org:
> On Mon, Nov 04, 2013 at 08:30:01PM +0000, xen@bugs.xenproject.org wrote:
Command failed: Unknown command `On''. at
/srv/xen-devel-bugs/lib/emesinae/control.pl line 437, <M> line 41.
Stop processing here.

---
Xen Hypervisor Bug Tracker
See http://wiki.xen.org/wiki/Reporting_Bugs_against_Xen for information on
reporting bugs
Contact xen-bugs-owner@bugs.xenproject.org with any infrastructure issues

On Mon, Nov 4, 2013 at 3:43 PM, Konrad Rzeszutek Wilk <
konrad.wilk@oracle.com> wrote:
>
> > Sure; this is your baby :)  Why don''t you handle it via your
tree,
> > since it''s more related to xen than any PCI core stuff.
> >
> > Acked-by: Bjorn Helgaas <bhelgaas@google.com>
>
> Definitly fixed in v3.12. Just tested it and it works.
>
> George, Ian, how do I "close" a bug in
> http://bugs.xenproject.org/xen/bug/12 ?
>
See doc here, for a HOWTO:
http://wiki.xen.org/wiki/Xen_Bug_Management_Interface#Closing_a_bug



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Processing commands for xen@bugs.xenproject.org:
> close 12
Closing bug #12
> 
Modified/created Bugs:
 - 12: http://bugs.xenproject.org/xen/bug/12

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