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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Xen-unstable-staging: Xen BUG at iommu_map.c:455
On 11/04/15 17:32, Andrew Cooper wrote:
> On 11/04/15 17:21, Sander Eikelenboom wrote:
>> Saturday, April 11, 2015, 4:21:56 PM, you wrote:
>>
>>> On 11/04/15 15:11, Sander Eikelenboom wrote:
>>>> Friday, April 10, 2015, 8:55:27 PM, you wrote:
>>>>
>>>>> On 10/04/15 11:24, Sander Eikelenboom wrote:
>>>>>> Hi Andrew,
>>>>>>
>>>>>> Finally got some time to figure this out .. and i have narrowed it down
>>>>>> to:
>>>>>> git://xenbits.xen.org/staging/qemu-upstream-unstable.git
>>>>>> commit 7665d6ba98e20fb05c420de947c1750fd47e5c07 "Xen: Use the
>>>>>> ioreq-server API when available"
>>>>>> A straight revert of this commit prevents the issue from happening.
>>>>>>
>>>>>> The reason i had a hard time figuring this out was:
>>>>>> - I wasn't aware of this earlier, since git pulling the main xen tree,
>>>>>> doesn't
>>>>>> auto update the qemu-* trees.
>>>>> This has caught me out so many times. It is very non-obvious behaviour.
>>>>>> - So i happen to get this when i cloned a fresh tree to try to figure
>>>>>> out the
>>>>>> other issue i was seeing.
>>>>>> - After that checking out previous versions of the main xen tree didn't
>>>>>> resolve
>>>>>> this new issue, because the qemu tree doesn't get auto updated and is
>>>>>> set
>>>>>> "master".
>>>>>> - Cloning a xen-stable-4.5.0 made it go away .. because that has a
>>>>>> specific
>>>>>> git://xenbits.xen.org/staging/qemu-upstream-unstable.git tag which is
>>>>>> not
>>>>>> master.
>>>>>>
>>>>>> *sigh*
>>>>>>
>>>>>> This is tested with xen main tree at last commit
>>>>>> 3a28f760508fb35c430edac17a9efde5aff6d1d5
>>>>>> (normal xen-unstable, not the staging branch)
>>>>>>
>>>>>> Ok so i have added some extra debug info (see attached diff) and this is
>>>>>> the
>>>>>> output when it crashes due to something the commit above triggered, the
>>>>>> level is out of bounds and the pfn looks fishy too.
>>>>>> Complete serial log from both bad and good (specific commit reverted)
>>>>>> are
>>>>>> attached.
>>>>> Just to confirm, you are positively identifying a qemu changeset as
>>>>> causing this crash?
>>>>> If so, the qemu change has discovered a pre-existing issue in the
>>>>> toolstack pci-passthrough interface. Whatever qemu is or isn't doing,
>>>>> it should not be able to cause a crash like this.
>>>>> With this in mind, I need to brush up on my AMD-Vi details.
>>>>> In the meantime, can you run with the following patch to identify what
>>>>> is going on, domctl wise? I assume it is the assign_device which is
>>>>> failing, but it will be nice to observe the differences between the
>>>>> working and failing case, which might offer a hint.
>>>> Hrrm with your patch i end up with a fatal page fault in
>>>> iommu_do_pci_domctl:
>>>>
>>>> (XEN) [2015-04-11 14:03:31.833] ----[ Xen-4.6-unstable x86_64 debug=y
>>>> Tainted: C ]----
>>>> (XEN) [2015-04-11 14:03:31.857] CPU: 5
>>>> (XEN) [2015-04-11 14:03:31.868] RIP: e008:[<ffff82d08014c52c>]
>>>> iommu_do_pci_domctl+0x2dc/0x740
>>>> (XEN) [2015-04-11 14:03:31.894] RFLAGS: 0000000000010256 CONTEXT:
>>>> hypervisor
>>>> (XEN) [2015-04-11 14:03:31.915] rax: 0000000000000008 rbx:
>>>> 0000000000000800 rcx: ffffffffffebe5ed
>>>> (XEN) [2015-04-11 14:03:31.942] rdx: 0000000000000800 rsi:
>>>> 0000000000000000 rdi: ffff830256ef7e38
>>>> (XEN) [2015-04-11 14:03:31.968] rbp: ffff830256ef7c98 rsp:
>>>> ffff830256ef7c08 r8: 00000000deadbeef
>>>> (XEN) [2015-04-11 14:03:31.995] r9: 00000000deadbeef r10:
>>>> ffff82d08024e500 r11: 0000000000000282
>>>> (XEN) [2015-04-11 14:03:32.022] r12: 0000000000000000 r13:
>>>> 0000000000000008 r14: 0000000000000000
>>>> (XEN) [2015-04-11 14:03:32.049] r15: 0000000000000000 cr0:
>>>> 0000000080050033 cr4: 00000000000006f0
>>>> (XEN) [2015-04-11 14:03:32.076] cr3: 00000002336a6000 cr2:
>>>> 0000000000000000
>>>> (XEN) [2015-04-11 14:03:32.096] ds: 0000 es: 0000 fs: 0000 gs: 0000
>>>> ss: e010 cs: e008
>>>> (XEN) [2015-04-11 14:03:32.121] Xen stack trace from rsp=ffff830256ef7c08:
>>>> (XEN) [2015-04-11 14:03:32.141] ffff830256ef7c78 ffff82d08012c178
>>>> ffff830256ef7c28 ffff830256ef7c28
>>>> (XEN) [2015-04-11 14:03:32.168] 0000000000000010 0000000000000000
>>>> 0000000000000000 0000000000000000
>>>> (XEN) [2015-04-11 14:03:32.195] 00000000000006f0 00007fe300000000
>>>> ffff830256eb7790 ffff83025cc6d300
>>>> (XEN) [2015-04-11 14:03:32.222] ffff82d080330c60 00007fe396bab004
>>>> 0000000000000000 00007fe396bab004
>>>> (XEN) [2015-04-11 14:03:32.249] 0000000000000000 0000000000000005
>>>> ffff830256ef7ca8 ffff82d08014900b
>>>> (XEN) [2015-04-11 14:03:32.276] ffff830256ef7d98 ffff82d080161f2d
>>>> 0000000000000010 0000000000000000
>>>> (XEN) [2015-04-11 14:03:32.303] 0000000000000000 ffff830256ef7ce8
>>>> ffff82d08018b655 ffff830256ef7d48
>>>> (XEN) [2015-04-11 14:03:32.330] ffff830256ef7cf8 ffff82d08018b66a
>>>> ffff830256ef7d38 ffff82d08012925e
>>>> (XEN) [2015-04-11 14:03:32.357] ffff830256efc068 0000000800000001
>>>> 800000022e12c167 0000000000000000
>>>> (XEN) [2015-04-11 14:03:32.384] 0000000000000002 ffff830256ef7e38
>>>> 0000000800000000 800000022e12c167
>>>> (XEN) [2015-04-11 14:03:32.411] 0000000000000003 ffff830256ef7db8
>>>> 0000000000000000 00007fe396780eb0
>>>> (XEN) [2015-04-11 14:03:32.439] 0000000000000202 ffffffffffffffff
>>>> 0000000000000000 00007fe396bab004
>>>> (XEN) [2015-04-11 14:03:32.466] 0000000000000000 0000000000000005
>>>> ffff830256ef7ef8 ffff82d08010497f
>>>> (XEN) [2015-04-11 14:03:32.493] 0000000000000001 0000000000100001
>>>> 800000022e12c167 ffff88001f7ecc00
>>>> (XEN) [2015-04-11 14:03:32.520] 00007fe396780eb0 ffff88001c849508
>>>> 0000000e00000007 ffffffff8105594a
>>>> (XEN) [2015-04-11 14:03:32.547] 000000000000e033 0000000000000202
>>>> ffff88001ece3d40 000000000000e02b
>>>> (XEN) [2015-04-11 14:03:32.574] ffff830256ef7e28 ffff82d080194933
>>>> 000000000000beef ffffffff81bd6c85
>>>> (XEN) [2015-04-11 14:03:32.601] ffff830256ef7f08 ffff82d080193edd
>>>> 0000000b0000002d 0000000000000001
>>>> (XEN) [2015-04-11 14:03:32.628] 0000000100000800 00007fe3962abbd0
>>>> ffff000a81050001 00007fe39656ce6e
>>>> (XEN) [2015-04-11 14:03:32.655] 00007ffdf2a654f0 00007fe39656d0c9
>>>> 00007fe39656ce6e 00007fe3969a9a55
>>>> (XEN) [2015-04-11 14:03:32.682] Xen call trace:
>>>> (XEN) [2015-04-11 14:03:32.695] [<ffff82d08014c52c>]
>>>> iommu_do_pci_domctl+0x2dc/0x740
>>>> (XEN) [2015-04-11 14:03:32.718] [<ffff82d08014900b>]
>>>> iommu_do_domctl+0x17/0x1a
>>>> (XEN) [2015-04-11 14:03:32.739] [<ffff82d080161f2d>]
>>>> arch_do_domctl+0x2469/0x26e1
>>>> (XEN) [2015-04-11 14:03:32.762] [<ffff82d08010497f>]
>>>> do_domctl+0x1a1f/0x1d60
>>>> (XEN) [2015-04-11 14:03:32.783] [<ffff82d080234c6b>]
>>>> syscall_enter+0xeb/0x145
>>>> (XEN) [2015-04-11 14:03:32.804]
>>>> (XEN) [2015-04-11 14:03:32.813] Pagetable walk from 0000000000000000:
>>>> (XEN) [2015-04-11 14:03:32.831] L4[0x000] = 0000000234075067
>>>> 000000000001f2a8
>>>> (XEN) [2015-04-11 14:03:32.852] L3[0x000] = 0000000229ad4067
>>>> 0000000000014c49
>>>> (XEN) [2015-04-11 14:03:32.873] L2[0x000] = 0000000000000000
>>>> ffffffffffffffff
>>>> (XEN) [2015-04-11 14:03:32.894]
>>>> (XEN) [2015-04-11 14:03:32.903] ****************************************
>>>> (XEN) [2015-04-11 14:03:32.922] Panic on CPU 5:
>>>> (XEN) [2015-04-11 14:03:32.935] FATAL PAGE FAULT
>>>> (XEN) [2015-04-11 14:03:32.948] [error_code=0000]
>>>> (XEN) [2015-04-11 14:03:32.961] Faulting linear address: 0000000000000000
>>>> (XEN) [2015-04-11 14:03:32.981] ****************************************
>>>> (XEN) [2015-04-11 14:03:33.000]
>>>> (XEN) [2015-04-11 14:03:33.009] Reboot in five seconds...
>>>>
>>>> The RIP resolves to the prink added by your patch in:
>>>>
>>>> case XEN_DOMCTL_test_assign_device:
>>>> ret = xsm_test_assign_device(XSM_HOOK,
>>>> domctl->u.assign_device.machine_sbdf);
>>>> if ( ret )
>>>> break;
>>>>
>>>> seg = domctl->u.assign_device.machine_sbdf >> 16;
>>>> bus = (domctl->u.assign_device.machine_sbdf >> 8) & 0xff;
>>>> devfn = domctl->u.assign_device.machine_sbdf & 0xff;
>>>>
>>>> printk("*** %pv->d%d: test_assign_device({%04x:%02x:%02x.%u})\n",
>>>> current, d->domain_id,
>>>> seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>>>>
>>>> if ( device_assigned(seg, bus, devfn) )
>>>> {
>>>> printk(XENLOG_G_INFO
>>>> "%04x:%02x:%02x.%u already assigned, or non-existent\n",
>>>> seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>>>> ret = -EINVAL;
>>>> }
>>>> break;
>>> hmm - 'd' is NULL. This ought to work better.
>>> diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
>>> index 9f3413c..85ff1fc 100644
>>> --- a/xen/drivers/passthrough/pci.c
>>> +++ b/xen/drivers/passthrough/pci.c
>>> @@ -1532,6 +1532,11 @@ int iommu_do_pci_domctl(
>>> max_sdevs = domctl->u.get_device_group.max_sdevs;
>>> sdevs = domctl->u.get_device_group.sdev_array;
>>>
>>> + printk("*** %pv->d%d: get_device_group({%04x:%02x:%02x.%u, %u})\n",
>>> + current, d->domain_id,
>>> + seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn),
>>> + max_sdevs);
>>> +
>>> ret = iommu_get_device_group(d, seg, bus, devfn, sdevs, max_sdevs);
>>> if ( ret < 0 )
>>> {
>>> @@ -1558,6 +1563,9 @@ int iommu_do_pci_domctl(
>>> bus = (domctl->u.assign_device.machine_sbdf >> 8) & 0xff;
>>> devfn = domctl->u.assign_device.machine_sbdf & 0xff;
>>>
>>> + printk("*** %pv: test_assign_device({%04x:%02x:%02x.%u})\n",
>>> + current, seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>>> +
>>> if ( device_assigned(seg, bus, devfn) )
>>> {
>>> printk(XENLOG_G_INFO
>>> @@ -1582,6 +1590,10 @@ int iommu_do_pci_domctl(
>>> bus = (domctl->u.assign_device.machine_sbdf >> 8) & 0xff;
>>> devfn = domctl->u.assign_device.machine_sbdf & 0xff;
>>>
>>> + printk("*** %pv->d%d: assign_device({%04x:%02x:%02x.%u})\n",
>>> + current, d->domain_id,
>>> + seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>>> +
>>> ret = device_assigned(seg, bus, devfn) ?:
>>> assign_device(d, seg, bus, devfn);
>>> if ( ret == -ERESTART )
>>> @@ -1604,6 +1616,10 @@ int iommu_do_pci_domctl(
>>> bus = (domctl->u.assign_device.machine_sbdf >> 8) & 0xff;
>>> devfn = domctl->u.assign_device.machine_sbdf & 0xff;
>>>
>>> + printk("*** %pv->d%d: deassign_device({%04x:%02x:%02x.%u})\n",
>>> + current, d->domain_id,
>>> + seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>>> +
>>> spin_lock(&pcidevs_lock);
>>> ret = deassign_device(d, seg, bus, devfn);
>>> spin_unlock(&pcidevs_lock);
>> Hi Andrew,
>>
>> Attached are the serial logs good (with revert) and bad (without):
>>
>> Some things that seems strange to me:
>> - The numerous calls to get the device 08:00.0 assigned ... for 0a:00.0
>> there
>> was only one call to both test assign and assign.
>> - However these numerous calls are there in both the good and the bad case,
>> so perhaps it's strange and wrong .. but not the cause ..
>> - I had a hunch it could be due to the 08:00.0 using MSI-X, but when only
>> passing through 0a:00.0, i get the same numerous calls but now for the
>> 0a:00.0 which uses IntX, so I think that is more related to being the
>> *first*
>> device to be passed through to a guest.
> I have also observed this behaviour, but not had time to investigate.
> It doesn't appear problematic in the longrun but it probably a toolstack
> issue which wants fixing (if only in the name of efficiency).
And just after I sent this email, I have realised why.
The first assign device will have to build IO pagetables, which is a
long operation and subject to hypercall continuations. The second
device will reused the same pagetables, so is quick to complete.
~Andrew
>
>> - On both the good and the bad case the "current" indicates more than one
>> vpcu
>> was used, so that doesn't seem to be a pointer either.
> That is to be expected. It will be whichever vcpu the toolstack process
> happened to be scheduled on at the point that it made the hypercall, and
> is liable to change at the whim of the dom0 scheduler.
>
>> - The bad log seems to indicate it crashes on or before hd->arch.paging_mode
>> gets to
>> 3.
>>
>> Is there anything useful to dump in update_paging_mode() when it updates the
>> paging mode to the invalid value (8)?
>> (and shouldn't that be denied in the first place ?)
>>
>> To me that looks like the first indication that things are starting to go
>> wrong.
> I would concur. I am currently trying to develop another debugging
> patch, but to do that I also what to understand what I am debugging,
> which is why I have the AMD-Vi spec open :)
>
> ~Andrew
>
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