Re: [Xen-devel] Xen pci-passthrough problem with pci-detach and pci-assignable-remove

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Apr 02, 2014 at 12:43:12PM +0200, Sander Eikelenboom wrote:
> 
> Tuesday, April 1, 2014, 6:13:09 PM, you wrote:
> 
> > On Thu, Feb 20, 2014 at 05:18:46PM +0100, Sander Eikelenboom wrote:
> >> 
> >> Thursday, February 20, 2014, 9:53:59 AM, you wrote:
> >> 
> >> 
> >> > Friday, January 24, 2014, 6:48:06 PM, you wrote:
> >> 
> >> >> On Fri, Jan 24, 2014 at 02:36:02PM +0100, Sander Eikelenboom wrote:
> >> >>> 
> >> >>> Friday, January 10, 2014, 6:38:10 PM, you wrote:
> >> >>> 
> >> >>> >> > Wow. You just walked in a pile of bugs didn't you? And on Friday
> >> >>> >> > nonethless.
> >> >>> >> 
> >> >>> >> As usual ;-)
> >> >>> 
> >> >>> > Ha!
> >> >>> > ..snip..
> >> >>> >> >> [  489.082358]  [<ffffffff81087ac6>] ? 
> >> >>> >> >> mutex_spin_on_owner+0x38/0x45
> >> >>> >> >> [  489.106272]  [<ffffffff818e5e22>] ? 
> >> >>> >> >> schedule_preempt_disabled+0x6/0x9
> >> >>> >> >> [  489.130158]  [<ffffffff818e7034>] ? 
> >> >>> >> >> __mutex_lock_slowpath+0x159/0x1b5
> >> >>> >> >> [  489.154147]  [<ffffffff818e70a6>] ? mutex_lock+0x16/0x25
> >> >>> >> >> [  489.177890]  [<ffffffff8135972d>] ? 
> >> >>> >> >> pci_reset_function+0x26/0x4e
> >> >>> >> 
> >> >>> >> > Yeah, that bug my RFC patchset (the one that does the slot/bus 
> >> >>> >> > reset) should also fix.
> >> >>> >> > I totally forgot about it !
> >> >>> >> 
> >> >>> >> Got a link to that patchset ?
> >> >>> 
> >> >>> > https://lkml.org/lkml/2013/12/13/315
> >> >>> 
> >> >>> >> I at least could give it a spin .. you never know when fortune is 
> >> >>> >> on your side :-)
> >> >>> 
> >> >>> > It is also at this git tree:
> >> >>> 
> >> >>> > git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git and the
> >> >>> > branch name is "devel/xen-pciback.slot_and_bus.v0". You will likely
> >> >>> > want to merge it in your current Linus tree.
> >> >>> 
> >> >>> > Thank you!
> >> >>> 
> >> >>> 
> >> >>> Hi Konrad,
> >> >>> 
> >> >>> Just got time to test this some more, when merging this branch 
> >> >>> *except* the last commit (9599a5ad38a3bb250e996ccb2cdaab6fb68aaacd)
> >> >>> seems to help with my problem,i'm no capable of using:
> >> >>> - xl pci-detach
> >> >>> - xl pci-assignable-remove
> >> >>> - echo "BDF" > /sys/bus/pci/drivers/<devicename>/bind
> >> >>> 
> >> >>> to remove a pci device from a running HVM guest and rebinding it to a 
> >> >>> driver in dom0 without those nasty stacktraces :-)
> >> >>> So the first 4 seem to be an improvement.
> >> >>> 
> >> >>> That last commit (9599a5ad38a3bb250e996ccb2cdaab6fb68aaacd) seems to 
> >> >>> give troubles of it's own.
> >> 
> >> >> Could you email me your lspci output and also which devices you 
> >> >> move/switch etc?
> >> 
> >> > Hi Konrad,
> >> 
> >> > At the moment i found some time to figure out what goes wrong with the 
> >> > xl pci-detach and xl pci-assignable-remove, i have been
> >> > able to narrow it down a bit:
> >> 
> >> > The problem only occurs when you:
> >> > - passthrough 2 (or more?) pci devices assigned to a guest ..
> >> > - and only remove 1 of those devices with "xl pci-detach" followed by a 
> >> > "xl pci-assignable-remove"
> >> > - when you first detach both devices with "xl pci-detach" before doing 
> >> > the "xl pci-assignable-remove" it works ok.
> >> 
> >> > In my case i'm passingthrough 2 devices (02:00.0 and 00:19.0)
> >> 
> >> > I added some printk's and what i found out is that:
> >> > - after doing the pci-detach of 02:00.0, it doesn't call 
> >> > pcistub_put_pci_dev for that device ...
> >> > - but when i subsequently pci-detach the second (and last) device 
> >> > 00:19.0 .. it does call it for both 02:00.0 and 00:19.0 ...
> >> > - so somehow that call for the first detached device gets deferred .. 
> >> > but since it are different devices and not functions of the same device 
> >> > i don't
> >> >   see any reason for it to wait until all other devices would have been 
> >> > detached ...
> >> 
> >> 
> >> > I tried to capture the console output but some how that didn't work out, 
> >> > so i attached a screenshot of what happens when:
> >> > - doing a xl pci-list for the guest
> >> > - doing a xl pci-assignable-list
> >> 
> >> > - doing the xl pci-detach for 02:00.0
> >> 
> >> > - doing a xl pci-list for the guest
> >> > - doing a xl pci-assignable-list
> >> 
> >> > - waiting some time ...
> >> 
> >> > - doing the xl pci-detach for 00:19.0
> >> 
> >> > - doing a xl pci-list for the guest
> >> > - doing a xl pci-assignable-list
> >> 
> >> > There you can see this strange sequence of events :-)
> >> 
> >> > But i haven't been able to spot the culprit
> >> 
> >> Enabled some extra debugging and added some more printk's .. (see new 
> >> screenshot)
> >> 
> >> From what it seems .. the frontend state for the first device isn't 
> >> changed on the first pci-detach ..
> >> 
> >> Is the signaling on pci-detach the guests (pcifront) responsibility or the 
> >> toolstacks (libxl) ?
> 
> > It usually is pcifront. And in the screenshot I see:
> > .. frontend is gone! unregister device
> > which should trigger the process. And it does look to do that.
> > Hm, I am wondering what the toolstack is waiting for.
> > Time to debug.
> 
> Ok thx :-)

Just to make sure - you are not using the xen-pciback.hide parameter right?
Just doing the /sysfs dance of 'echo BDF'> to various places.

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